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, 2018 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 uint32_t zfs_vdev_initializing_min_active = 1;
154 uint32_t zfs_vdev_initializing_max_active = 1;
155
156 /*
157 * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent
158 * dirty data, use zfs_vdev_async_write_min_active. When it has more than
159 * zfs_vdev_async_write_active_max_dirty_percent, use
160 * zfs_vdev_async_write_max_active. The value is linearly interpolated
161 * between min and max.
162 */
163 int zfs_vdev_async_write_active_min_dirty_percent = 30;
164 int zfs_vdev_async_write_active_max_dirty_percent = 60;
165
166 /*
167 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
168 * For read I/Os, we also aggregate across small adjacency gaps; for writes
169 * we include spans of optional I/Os to aid aggregation at the disk even when
170 * they aren't able to help us aggregate at this level.
171 */
172 int zfs_vdev_aggregation_limit = 1 << 20;
173 int zfs_vdev_read_gap_limit = 32 << 10;
174 int zfs_vdev_write_gap_limit = 4 << 10;
175
176 /*
177 * Define the queue depth percentage for each top-level. This percentage is
178 * used in conjunction with zfs_vdev_async_max_active to determine how many
179 * allocations a specific top-level vdev should handle. Once the queue depth
180 * reaches zfs_vdev_queue_depth_pct * zfs_vdev_async_write_max_active / 100
181 * then allocator will stop allocating blocks on that top-level device.
182 * The default kernel setting is 1000% which will yield 100 allocations per
183 * device. For userland testing, the default setting is 300% which equates
184 * to 30 allocations per device.
185 */
186 #ifdef _KERNEL
187 int zfs_vdev_queue_depth_pct = 1000;
188 #else
189 int zfs_vdev_queue_depth_pct = 300;
190 #endif
191
192 /*
193 * When performing allocations for a given metaslab, we want to make sure that
194 * there are enough IOs to aggregate together to improve throughput. We want to
195 * ensure that there are at least 128k worth of IOs that can be aggregated, and
196 * we assume that the average allocation size is 4k, so we need the queue depth
197 * to be 32 per allocator to get good aggregation of sequential writes.
198 */
199 int zfs_vdev_def_queue_depth = 32;
200
201
202 int
203 vdev_queue_offset_compare(const void *x1, const void *x2)
204 {
205 const zio_t *z1 = (const zio_t *)x1;
206 const zio_t *z2 = (const zio_t *)x2;
207
208 int cmp = AVL_CMP(z1->io_offset, z2->io_offset);
209
210 if (likely(cmp))
211 return (cmp);
212
213 return (AVL_PCMP(z1, z2));
214 }
215
216 static inline avl_tree_t *
217 vdev_queue_class_tree(vdev_queue_t *vq, zio_priority_t p)
218 {
219 return (&vq->vq_class[p].vqc_queued_tree);
220 }
221
222 static inline avl_tree_t *
223 vdev_queue_type_tree(vdev_queue_t *vq, zio_type_t t)
224 {
225 ASSERT(t == ZIO_TYPE_READ || t == ZIO_TYPE_WRITE);
226 if (t == ZIO_TYPE_READ)
227 return (&vq->vq_read_offset_tree);
228 else
229 return (&vq->vq_write_offset_tree);
230 }
231
232 int
233 vdev_queue_timestamp_compare(const void *x1, const void *x2)
234 {
235 const zio_t *z1 = (const zio_t *)x1;
236 const zio_t *z2 = (const zio_t *)x2;
237
238 int cmp = AVL_CMP(z1->io_timestamp, z2->io_timestamp);
239
240 if (likely(cmp))
241 return (cmp);
242
243 return (AVL_PCMP(z1, z2));
244 }
245
246 void
247 vdev_queue_init(vdev_t *vd)
248 {
249 vdev_queue_t *vq = &vd->vdev_queue;
250
251 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
252 vq->vq_vdev = vd;
253
254 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare,
255 sizeof (zio_t), offsetof(struct zio, io_queue_node));
256 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_READ),
257 vdev_queue_offset_compare, sizeof (zio_t),
258 offsetof(struct zio, io_offset_node));
259 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE),
260 vdev_queue_offset_compare, sizeof (zio_t),
261 offsetof(struct zio, io_offset_node));
262
263 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
264 int (*compfn) (const void *, const void *);
265
266 /*
267 * The synchronous i/o queues are dispatched in FIFO rather
268 * than LBA order. This provides more consistent latency for
269 * these i/os.
270 */
271 if (p == ZIO_PRIORITY_SYNC_READ || p == ZIO_PRIORITY_SYNC_WRITE)
272 compfn = vdev_queue_timestamp_compare;
273 else
274 compfn = vdev_queue_offset_compare;
275
276 avl_create(vdev_queue_class_tree(vq, p), compfn,
277 sizeof (zio_t), offsetof(struct zio, io_queue_node));
278 }
279
280 vq->vq_last_offset = 0;
281 }
282
283 void
284 vdev_queue_fini(vdev_t *vd)
285 {
286 vdev_queue_t *vq = &vd->vdev_queue;
287
288 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
289 avl_destroy(vdev_queue_class_tree(vq, p));
290 avl_destroy(&vq->vq_active_tree);
291 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_READ));
292 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE));
293
294 mutex_destroy(&vq->vq_lock);
295 }
296
297 static void
298 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
299 {
300 spa_t *spa = zio->io_spa;
301
302 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
303 avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);
304 avl_add(vdev_queue_type_tree(vq, zio->io_type), zio);
305
306 mutex_enter(&spa->spa_iokstat_lock);
307 spa->spa_queue_stats[zio->io_priority].spa_queued++;
308 if (spa->spa_iokstat != NULL)
309 kstat_waitq_enter(spa->spa_iokstat->ks_data);
310 mutex_exit(&spa->spa_iokstat_lock);
311 }
312
313 static void
314 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
315 {
316 spa_t *spa = zio->io_spa;
317
318 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
319 avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
320 avl_remove(vdev_queue_type_tree(vq, zio->io_type), zio);
321
322 mutex_enter(&spa->spa_iokstat_lock);
323 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0);
324 spa->spa_queue_stats[zio->io_priority].spa_queued--;
325 if (spa->spa_iokstat != NULL)
326 kstat_waitq_exit(spa->spa_iokstat->ks_data);
327 mutex_exit(&spa->spa_iokstat_lock);
328 }
329
330 static void
331 vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio)
332 {
333 spa_t *spa = zio->io_spa;
334 ASSERT(MUTEX_HELD(&vq->vq_lock));
335 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
336 vq->vq_class[zio->io_priority].vqc_active++;
337 avl_add(&vq->vq_active_tree, zio);
338
339 mutex_enter(&spa->spa_iokstat_lock);
340 spa->spa_queue_stats[zio->io_priority].spa_active++;
341 if (spa->spa_iokstat != NULL)
342 kstat_runq_enter(spa->spa_iokstat->ks_data);
343 mutex_exit(&spa->spa_iokstat_lock);
344 }
345
346 static void
347 vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio)
348 {
349 spa_t *spa = zio->io_spa;
350 ASSERT(MUTEX_HELD(&vq->vq_lock));
351 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
352 vq->vq_class[zio->io_priority].vqc_active--;
353 avl_remove(&vq->vq_active_tree, zio);
354
355 mutex_enter(&spa->spa_iokstat_lock);
356 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0);
357 spa->spa_queue_stats[zio->io_priority].spa_active--;
358 if (spa->spa_iokstat != NULL) {
359 kstat_io_t *ksio = spa->spa_iokstat->ks_data;
360
361 kstat_runq_exit(spa->spa_iokstat->ks_data);
362 if (zio->io_type == ZIO_TYPE_READ) {
363 ksio->reads++;
364 ksio->nread += zio->io_size;
365 } else if (zio->io_type == ZIO_TYPE_WRITE) {
366 ksio->writes++;
367 ksio->nwritten += zio->io_size;
368 }
369 }
370 mutex_exit(&spa->spa_iokstat_lock);
371 }
372
373 static void
374 vdev_queue_agg_io_done(zio_t *aio)
375 {
376 if (aio->io_type == ZIO_TYPE_READ) {
377 zio_t *pio;
378 zio_link_t *zl = NULL;
379 while ((pio = zio_walk_parents(aio, &zl)) != NULL) {
380 abd_copy_off(pio->io_abd, aio->io_abd,
381 0, pio->io_offset - aio->io_offset, pio->io_size);
382 }
383 }
384
385 abd_free(aio->io_abd);
386 }
387
388 static int
389 vdev_queue_class_min_active(zio_priority_t p)
390 {
391 switch (p) {
392 case ZIO_PRIORITY_SYNC_READ:
393 return (zfs_vdev_sync_read_min_active);
394 case ZIO_PRIORITY_SYNC_WRITE:
395 return (zfs_vdev_sync_write_min_active);
396 case ZIO_PRIORITY_ASYNC_READ:
397 return (zfs_vdev_async_read_min_active);
398 case ZIO_PRIORITY_ASYNC_WRITE:
399 return (zfs_vdev_async_write_min_active);
400 case ZIO_PRIORITY_SCRUB:
401 return (zfs_vdev_scrub_min_active);
402 case ZIO_PRIORITY_REMOVAL:
403 return (zfs_vdev_removal_min_active);
404 case ZIO_PRIORITY_INITIALIZING:
405 return (zfs_vdev_initializing_min_active);
406 default:
407 panic("invalid priority %u", p);
408 return (0);
409 }
410 }
411
412 static int
413 vdev_queue_max_async_writes(spa_t *spa)
414 {
415 int writes;
416 uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total;
417 uint64_t min_bytes = zfs_dirty_data_max *
418 zfs_vdev_async_write_active_min_dirty_percent / 100;
419 uint64_t max_bytes = zfs_dirty_data_max *
420 zfs_vdev_async_write_active_max_dirty_percent / 100;
421
422 /*
423 * Sync tasks correspond to interactive user actions. To reduce the
424 * execution time of those actions we push data out as fast as possible.
425 */
426 if (spa_has_pending_synctask(spa)) {
427 return (zfs_vdev_async_write_max_active);
428 }
429
430 if (dirty < min_bytes)
431 return (zfs_vdev_async_write_min_active);
432 if (dirty > max_bytes)
433 return (zfs_vdev_async_write_max_active);
434
435 /*
436 * linear interpolation:
437 * slope = (max_writes - min_writes) / (max_bytes - min_bytes)
438 * move right by min_bytes
439 * move up by min_writes
440 */
441 writes = (dirty - min_bytes) *
442 (zfs_vdev_async_write_max_active -
443 zfs_vdev_async_write_min_active) /
444 (max_bytes - min_bytes) +
445 zfs_vdev_async_write_min_active;
446 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active);
447 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active);
448 return (writes);
449 }
450
451 static int
452 vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
453 {
454 switch (p) {
455 case ZIO_PRIORITY_SYNC_READ:
456 return (zfs_vdev_sync_read_max_active);
457 case ZIO_PRIORITY_SYNC_WRITE:
458 return (zfs_vdev_sync_write_max_active);
459 case ZIO_PRIORITY_ASYNC_READ:
460 return (zfs_vdev_async_read_max_active);
461 case ZIO_PRIORITY_ASYNC_WRITE:
462 return (vdev_queue_max_async_writes(spa));
463 case ZIO_PRIORITY_SCRUB:
464 return (zfs_vdev_scrub_max_active);
465 case ZIO_PRIORITY_REMOVAL:
466 return (zfs_vdev_removal_max_active);
467 case ZIO_PRIORITY_INITIALIZING:
468 return (zfs_vdev_initializing_max_active);
469 default:
470 panic("invalid priority %u", p);
471 return (0);
472 }
473 }
474
475 /*
476 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if
477 * there is no eligible class.
478 */
479 static zio_priority_t
480 vdev_queue_class_to_issue(vdev_queue_t *vq)
481 {
482 spa_t *spa = vq->vq_vdev->vdev_spa;
483 zio_priority_t p;
484
485 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active)
486 return (ZIO_PRIORITY_NUM_QUEUEABLE);
487
488 /* find a queue that has not reached its minimum # outstanding i/os */
489 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
490 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
491 vq->vq_class[p].vqc_active <
492 vdev_queue_class_min_active(p))
493 return (p);
494 }
495
496 /*
497 * If we haven't found a queue, look for one that hasn't reached its
498 * maximum # outstanding i/os.
499 */
500 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
501 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
502 vq->vq_class[p].vqc_active <
503 vdev_queue_class_max_active(spa, p))
504 return (p);
505 }
506
507 /* No eligible queued i/os */
508 return (ZIO_PRIORITY_NUM_QUEUEABLE);
509 }
510
511 /*
512 * Compute the range spanned by two i/os, which is the endpoint of the last
513 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
514 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
515 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
516 */
517 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
518 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
519
520 static zio_t *
521 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
522 {
523 zio_t *first, *last, *aio, *dio, *mandatory, *nio;
524 zio_link_t *zl = NULL;
525 uint64_t maxgap = 0;
526 uint64_t size;
527 boolean_t stretch = B_FALSE;
528 avl_tree_t *t = vdev_queue_type_tree(vq, zio->io_type);
529 enum zio_flag flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT;
530
531 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE)
532 return (NULL);
533
534 first = last = zio;
535
536 if (zio->io_type == ZIO_TYPE_READ)
537 maxgap = zfs_vdev_read_gap_limit;
538
539 /*
540 * We can aggregate I/Os that are sufficiently adjacent and of
541 * the same flavor, as expressed by the AGG_INHERIT flags.
542 * The latter requirement is necessary so that certain
543 * attributes of the I/O, such as whether it's a normal I/O
544 * or a scrub/resilver, can be preserved in the aggregate.
545 * We can include optional I/Os, but don't allow them
546 * to begin a range as they add no benefit in that situation.
547 */
548
549 /*
550 * We keep track of the last non-optional I/O.
551 */
552 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first;
553
554 /*
555 * Walk backwards through sufficiently contiguous I/Os
556 * recording the last non-optional I/O.
557 */
558 while ((dio = AVL_PREV(t, first)) != NULL &&
559 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
560 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit &&
561 IO_GAP(dio, first) <= maxgap &&
562 dio->io_type == zio->io_type) {
563 first = dio;
564 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL))
565 mandatory = first;
566 }
567
568 /*
569 * Skip any initial optional I/Os.
570 */
571 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) {
572 first = AVL_NEXT(t, first);
573 ASSERT(first != NULL);
574 }
575
576 /*
577 * Walk forward through sufficiently contiguous I/Os.
578 * The aggregation limit does not apply to optional i/os, so that
579 * we can issue contiguous writes even if they are larger than the
580 * aggregation limit.
581 */
582 while ((dio = AVL_NEXT(t, last)) != NULL &&
583 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
584 (IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit ||
585 (dio->io_flags & ZIO_FLAG_OPTIONAL)) &&
586 IO_GAP(last, dio) <= maxgap &&
587 dio->io_type == zio->io_type) {
588 last = dio;
589 if (!(last->io_flags & ZIO_FLAG_OPTIONAL))
590 mandatory = last;
591 }
592
593 /*
594 * Now that we've established the range of the I/O aggregation
595 * we must decide what to do with trailing optional I/Os.
596 * For reads, there's nothing to do. While we are unable to
597 * aggregate further, it's possible that a trailing optional
598 * I/O would allow the underlying device to aggregate with
599 * subsequent I/Os. We must therefore determine if the next
600 * non-optional I/O is close enough to make aggregation
601 * worthwhile.
602 */
603 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) {
604 zio_t *nio = last;
605 while ((dio = AVL_NEXT(t, nio)) != NULL &&
606 IO_GAP(nio, dio) == 0 &&
607 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) {
608 nio = dio;
609 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
610 stretch = B_TRUE;
611 break;
612 }
613 }
614 }
615
616 if (stretch) {
617 /*
618 * We are going to include an optional io in our aggregated
619 * span, thus closing the write gap. Only mandatory i/os can
620 * start aggregated spans, so make sure that the next i/o
621 * after our span is mandatory.
622 */
623 dio = AVL_NEXT(t, last);
624 dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
625 } else {
626 /* do not include the optional i/o */
627 while (last != mandatory && last != first) {
628 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL);
629 last = AVL_PREV(t, last);
630 ASSERT(last != NULL);
631 }
632 }
633
634 if (first == last)
635 return (NULL);
636
637 size = IO_SPAN(first, last);
638 ASSERT3U(size, <=, SPA_MAXBLOCKSIZE);
639
640 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset,
641 abd_alloc_for_io(size, B_TRUE), size, first->io_type,
642 zio->io_priority, flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
643 vdev_queue_agg_io_done, NULL);
644 aio->io_timestamp = first->io_timestamp;
645
646 nio = first;
647 do {
648 dio = nio;
649 nio = AVL_NEXT(t, dio);
650 ASSERT3U(dio->io_type, ==, aio->io_type);
651
652 if (dio->io_flags & ZIO_FLAG_NODATA) {
653 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE);
654 abd_zero_off(aio->io_abd,
655 dio->io_offset - aio->io_offset, dio->io_size);
656 } else if (dio->io_type == ZIO_TYPE_WRITE) {
657 abd_copy_off(aio->io_abd, dio->io_abd,
658 dio->io_offset - aio->io_offset, 0, dio->io_size);
659 }
660
661 zio_add_child(dio, aio);
662 vdev_queue_io_remove(vq, dio);
663 } while (dio != last);
664
665 /*
666 * We need to drop the vdev queue's lock to avoid a deadlock that we
667 * could encounter since this I/O will complete immediately.
668 */
669 mutex_exit(&vq->vq_lock);
670 while ((dio = zio_walk_parents(aio, &zl)) != NULL) {
671 zio_vdev_io_bypass(dio);
672 zio_execute(dio);
673 }
674 mutex_enter(&vq->vq_lock);
675
676 return (aio);
677 }
678
679 static zio_t *
680 vdev_queue_io_to_issue(vdev_queue_t *vq)
681 {
682 zio_t *zio, *aio;
683 zio_priority_t p;
684 avl_index_t idx;
685 avl_tree_t *tree;
686 zio_t search;
687
688 again:
689 ASSERT(MUTEX_HELD(&vq->vq_lock));
690
691 p = vdev_queue_class_to_issue(vq);
692
693 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) {
694 /* No eligible queued i/os */
695 return (NULL);
696 }
697
698 /*
699 * For LBA-ordered queues (async / scrub / initializing), issue the
700 * i/o which follows the most recently issued i/o in LBA (offset) order.
701 *
702 * For FIFO queues (sync), issue the i/o with the lowest timestamp.
703 */
704 tree = vdev_queue_class_tree(vq, p);
705 search.io_timestamp = 0;
706 search.io_offset = vq->vq_last_offset - 1;
707 VERIFY3P(avl_find(tree, &search, &idx), ==, NULL);
708 zio = avl_nearest(tree, idx, AVL_AFTER);
709 if (zio == NULL)
710 zio = avl_first(tree);
711 ASSERT3U(zio->io_priority, ==, p);
712
713 aio = vdev_queue_aggregate(vq, zio);
714 if (aio != NULL)
715 zio = aio;
716 else
717 vdev_queue_io_remove(vq, zio);
718
719 /*
720 * If the I/O is or was optional and therefore has no data, we need to
721 * simply discard it. We need to drop the vdev queue's lock to avoid a
722 * deadlock that we could encounter since this I/O will complete
723 * immediately.
724 */
725 if (zio->io_flags & ZIO_FLAG_NODATA) {
726 mutex_exit(&vq->vq_lock);
727 zio_vdev_io_bypass(zio);
728 zio_execute(zio);
729 mutex_enter(&vq->vq_lock);
730 goto again;
731 }
732
733 vdev_queue_pending_add(vq, zio);
734 vq->vq_last_offset = zio->io_offset + zio->io_size;
735
736 return (zio);
737 }
738
739 zio_t *
740 vdev_queue_io(zio_t *zio)
741 {
742 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
743 zio_t *nio;
744
745 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
746 return (zio);
747
748 /*
749 * Children i/os inherent their parent's priority, which might
750 * not match the child's i/o type. Fix it up here.
751 */
752 if (zio->io_type == ZIO_TYPE_READ) {
753 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ &&
754 zio->io_priority != ZIO_PRIORITY_ASYNC_READ &&
755 zio->io_priority != ZIO_PRIORITY_SCRUB &&
756 zio->io_priority != ZIO_PRIORITY_REMOVAL &&
757 zio->io_priority != ZIO_PRIORITY_INITIALIZING)
758 zio->io_priority = ZIO_PRIORITY_ASYNC_READ;
759 } else {
760 ASSERT(zio->io_type == ZIO_TYPE_WRITE);
761 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE &&
762 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE &&
763 zio->io_priority != ZIO_PRIORITY_REMOVAL &&
764 zio->io_priority != ZIO_PRIORITY_INITIALIZING)
765 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE;
766 }
767
768 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
769
770 mutex_enter(&vq->vq_lock);
771 zio->io_timestamp = gethrtime();
772 vdev_queue_io_add(vq, zio);
773 nio = vdev_queue_io_to_issue(vq);
774 mutex_exit(&vq->vq_lock);
775
776 if (nio == NULL)
777 return (NULL);
778
779 if (nio->io_done == vdev_queue_agg_io_done) {
780 zio_nowait(nio);
781 return (NULL);
782 }
783
784 return (nio);
785 }
786
787 void
788 vdev_queue_io_done(zio_t *zio)
789 {
790 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
791 zio_t *nio;
792
793 mutex_enter(&vq->vq_lock);
794
795 vdev_queue_pending_remove(vq, zio);
796
797 vq->vq_io_complete_ts = gethrtime();
798
799 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
800 mutex_exit(&vq->vq_lock);
801 if (nio->io_done == vdev_queue_agg_io_done) {
802 zio_nowait(nio);
803 } else {
804 zio_vdev_io_reissue(nio);
805 zio_execute(nio);
806 }
807 mutex_enter(&vq->vq_lock);
808 }
809
810 mutex_exit(&vq->vq_lock);
811 }
812
813 void
814 vdev_queue_change_io_priority(zio_t *zio, zio_priority_t priority)
815 {
816 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
817 avl_tree_t *tree;
818
819 /*
820 * ZIO_PRIORITY_NOW is used by the vdev cache code and the aggregate zio
821 * code to issue IOs without adding them to the vdev queue. In this
822 * case, the zio is already going to be issued as quickly as possible
823 * and so it doesn't need any reprioitization to help.
824 */
825 if (zio->io_priority == ZIO_PRIORITY_NOW)
826 return;
827
828 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
829 ASSERT3U(priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
830
831 if (zio->io_type == ZIO_TYPE_READ) {
832 if (priority != ZIO_PRIORITY_SYNC_READ &&
833 priority != ZIO_PRIORITY_ASYNC_READ &&
834 priority != ZIO_PRIORITY_SCRUB)
835 priority = ZIO_PRIORITY_ASYNC_READ;
836 } else {
837 ASSERT(zio->io_type == ZIO_TYPE_WRITE);
838 if (priority != ZIO_PRIORITY_SYNC_WRITE &&
839 priority != ZIO_PRIORITY_ASYNC_WRITE)
840 priority = ZIO_PRIORITY_ASYNC_WRITE;
841 }
842
843 mutex_enter(&vq->vq_lock);
844
845 /*
846 * If the zio is in none of the queues we can simply change
847 * the priority. If the zio is waiting to be submitted we must
848 * remove it from the queue and re-insert it with the new priority.
849 * Otherwise, the zio is currently active and we cannot change its
850 * priority.
851 */
852 tree = vdev_queue_class_tree(vq, zio->io_priority);
853 if (avl_find(tree, zio, NULL) == zio) {
854 spa_t *spa = zio->io_spa;
855 zio_priority_t oldpri = zio->io_priority;
856
857 avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
858 zio->io_priority = priority;
859 avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);
860
861 mutex_enter(&spa->spa_iokstat_lock);
862 ASSERT3U(spa->spa_queue_stats[oldpri].spa_queued, >, 0);
863 spa->spa_queue_stats[oldpri].spa_queued--;
864 spa->spa_queue_stats[zio->io_priority].spa_queued++;
865 mutex_exit(&spa->spa_iokstat_lock);
866 } else if (avl_find(&vq->vq_active_tree, zio, NULL) != zio) {
867 zio->io_priority = priority;
868 }
869
870 mutex_exit(&vq->vq_lock);
871 }
872
873 /*
874 * As these two methods are only used for load calculations we're not
875 * concerned if we get an incorrect value on 32bit platforms due to lack of
876 * vq_lock mutex use here, instead we prefer to keep it lock free for
877 * performance.
878 */
879 int
880 vdev_queue_length(vdev_t *vd)
881 {
882 return (avl_numnodes(&vd->vdev_queue.vq_active_tree));
883 }
884
885 uint64_t
886 vdev_queue_last_offset(vdev_t *vd)
887 {
888 return (vd->vdev_queue.vq_last_offset);
889 }