xref: /illumos-gate/usr/src/uts/common/fs/zfs/vdev_queue.c (revision dd50e0cc4cbe1474096300fe52e9855769c0d478)
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  * Copyright 2019 Joyent, Inc.
30  */
31 
32 #include <sys/zfs_context.h>
33 #include <sys/vdev_impl.h>
34 #include <sys/spa_impl.h>
35 #include <sys/zio.h>
36 #include <sys/avl.h>
37 #include <sys/dsl_pool.h>
38 #include <sys/metaslab_impl.h>
39 #include <sys/abd.h>
40 
41 /*
42  * ZFS I/O Scheduler
43  * ---------------
44  *
45  * ZFS issues I/O operations to leaf vdevs to satisfy and complete zios.  The
46  * I/O scheduler determines when and in what order those operations are
47  * issued.  The I/O scheduler divides operations into five I/O classes
48  * prioritized in the following order: sync read, sync write, async read,
49  * async write, and scrub/resilver.  Each queue defines the minimum and
50  * maximum number of concurrent operations that may be issued to the device.
51  * In addition, the device has an aggregate maximum. Note that the sum of the
52  * per-queue minimums must not exceed the aggregate maximum, and if the
53  * aggregate maximum is equal to or greater than the sum of the per-queue
54  * maximums, the per-queue minimum has no effect.
55  *
56  * For many physical devices, throughput increases with the number of
57  * concurrent operations, but latency typically suffers. Further, physical
58  * devices typically have a limit at which more concurrent operations have no
59  * effect on throughput or can actually cause it to decrease.
60  *
61  * The scheduler selects the next operation to issue by first looking for an
62  * I/O class whose minimum has not been satisfied. Once all are satisfied and
63  * the aggregate maximum has not been hit, the scheduler looks for classes
64  * whose maximum has not been satisfied. Iteration through the I/O classes is
65  * done in the order specified above. No further operations are issued if the
66  * aggregate maximum number of concurrent operations has been hit or if there
67  * are no operations queued for an I/O class that has not hit its maximum.
68  * Every time an i/o is queued or an operation completes, the I/O scheduler
69  * looks for new operations to issue.
70  *
71  * All I/O classes have a fixed maximum number of outstanding operations
72  * except for the async write class. Asynchronous writes represent the data
73  * that is committed to stable storage during the syncing stage for
74  * transaction groups (see txg.c). Transaction groups enter the syncing state
75  * periodically so the number of queued async writes will quickly burst up and
76  * then bleed down to zero. Rather than servicing them as quickly as possible,
77  * the I/O scheduler changes the maximum number of active async write i/os
78  * according to the amount of dirty data in the pool (see dsl_pool.c). Since
79  * both throughput and latency typically increase with the number of
80  * concurrent operations issued to physical devices, reducing the burstiness
81  * in the number of concurrent operations also stabilizes the response time of
82  * operations from other -- and in particular synchronous -- queues. In broad
83  * strokes, the I/O scheduler will issue more concurrent operations from the
84  * async write queue as there's more dirty data in the pool.
85  *
86  * Async Writes
87  *
88  * The number of concurrent operations issued for the async write I/O class
89  * follows a piece-wise linear function defined by a few adjustable points.
90  *
91  *        |                   o---------| <-- zfs_vdev_async_write_max_active
92  *   ^    |                  /^         |
93  *   |    |                 / |         |
94  * active |                /  |         |
95  *  I/O   |               /   |         |
96  * count  |              /    |         |
97  *        |             /     |         |
98  *        |------------o      |         | <-- zfs_vdev_async_write_min_active
99  *       0|____________^______|_________|
100  *        0%           |      |       100% of zfs_dirty_data_max
101  *                     |      |
102  *                     |      `-- zfs_vdev_async_write_active_max_dirty_percent
103  *                     `--------- zfs_vdev_async_write_active_min_dirty_percent
104  *
105  * Until the amount of dirty data exceeds a minimum percentage of the dirty
106  * data allowed in the pool, the I/O scheduler will limit the number of
107  * concurrent operations to the minimum. As that threshold is crossed, the
108  * number of concurrent operations issued increases linearly to the maximum at
109  * the specified maximum percentage of the dirty data allowed in the pool.
110  *
111  * Ideally, the amount of dirty data on a busy pool will stay in the sloped
112  * part of the function between zfs_vdev_async_write_active_min_dirty_percent
113  * and zfs_vdev_async_write_active_max_dirty_percent. If it exceeds the
114  * maximum percentage, this indicates that the rate of incoming data is
115  * greater than the rate that the backend storage can handle. In this case, we
116  * must further throttle incoming writes (see dmu_tx_delay() for details).
117  */
118 
119 /*
120  * The maximum number of i/os active to each device.  Ideally, this will be >=
121  * the sum of each queue's max_active.  It must be at least the sum of each
122  * queue's min_active.
123  */
124 uint32_t zfs_vdev_max_active = 1000;
125 
126 /*
127  * Per-queue limits on the number of i/os active to each device.  If the
128  * sum of the queue's max_active is < zfs_vdev_max_active, then the
129  * min_active comes into play.  We will send min_active from each queue,
130  * and then select from queues in the order defined by zio_priority_t.
131  *
132  * In general, smaller max_active's will lead to lower latency of synchronous
133  * operations.  Larger max_active's may lead to higher overall throughput,
134  * depending on underlying storage.
135  *
136  * The ratio of the queues' max_actives determines the balance of performance
137  * between reads, writes, and scrubs.  E.g., increasing
138  * zfs_vdev_scrub_max_active will cause the scrub or resilver to complete
139  * more quickly, but reads and writes to have higher latency and lower
140  * throughput.
141  */
142 uint32_t zfs_vdev_sync_read_min_active = 10;
143 uint32_t zfs_vdev_sync_read_max_active = 10;
144 uint32_t zfs_vdev_sync_write_min_active = 10;
145 uint32_t zfs_vdev_sync_write_max_active = 10;
146 uint32_t zfs_vdev_async_read_min_active = 1;
147 uint32_t zfs_vdev_async_read_max_active = 3;
148 uint32_t zfs_vdev_async_write_min_active = 1;
149 uint32_t zfs_vdev_async_write_max_active = 10;
150 uint32_t zfs_vdev_scrub_min_active = 1;
151 uint32_t zfs_vdev_scrub_max_active = 2;
152 uint32_t zfs_vdev_removal_min_active = 1;
153 uint32_t zfs_vdev_removal_max_active = 2;
154 uint32_t zfs_vdev_initializing_min_active = 1;
155 uint32_t zfs_vdev_initializing_max_active = 1;
156 uint32_t zfs_vdev_trim_min_active = 1;
157 uint32_t zfs_vdev_trim_max_active = 2;
158 
159 /*
160  * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent
161  * dirty data, use zfs_vdev_async_write_min_active.  When it has more than
162  * zfs_vdev_async_write_active_max_dirty_percent, use
163  * zfs_vdev_async_write_max_active. The value is linearly interpolated
164  * between min and max.
165  */
166 int zfs_vdev_async_write_active_min_dirty_percent = 30;
167 int zfs_vdev_async_write_active_max_dirty_percent = 60;
168 
169 /*
170  * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
171  * For read I/Os, we also aggregate across small adjacency gaps; for writes
172  * we include spans of optional I/Os to aid aggregation at the disk even when
173  * they aren't able to help us aggregate at this level.
174  */
175 int zfs_vdev_aggregation_limit = 1 << 20;
176 int zfs_vdev_read_gap_limit = 32 << 10;
177 int zfs_vdev_write_gap_limit = 4 << 10;
178 
179 /*
180  * Define the queue depth percentage for each top-level. This percentage is
181  * used in conjunction with zfs_vdev_async_max_active to determine how many
182  * allocations a specific top-level vdev should handle. Once the queue depth
183  * reaches zfs_vdev_queue_depth_pct * zfs_vdev_async_write_max_active / 100
184  * then allocator will stop allocating blocks on that top-level device.
185  * The default kernel setting is 1000% which will yield 100 allocations per
186  * device. For userland testing, the default setting is 300% which equates
187  * to 30 allocations per device.
188  */
189 #ifdef _KERNEL
190 int zfs_vdev_queue_depth_pct = 1000;
191 #else
192 int zfs_vdev_queue_depth_pct = 300;
193 #endif
194 
195 /*
196  * When performing allocations for a given metaslab, we want to make sure that
197  * there are enough IOs to aggregate together to improve throughput. We want to
198  * ensure that there are at least 128k worth of IOs that can be aggregated, and
199  * we assume that the average allocation size is 4k, so we need the queue depth
200  * to be 32 per allocator to get good aggregation of sequential writes.
201  */
202 int zfs_vdev_def_queue_depth = 32;
203 
204 /*
205  * Allow TRIM I/Os to be aggregated.  This should normally not be needed since
206  * TRIM I/O for extents up to zfs_trim_extent_bytes_max (128M) can be submitted
207  * by the TRIM code in zfs_trim.c.
208  */
209 int zfs_vdev_aggregate_trim = 0;
210 
211 int
vdev_queue_offset_compare(const void * x1,const void * x2)212 vdev_queue_offset_compare(const void *x1, const void *x2)
213 {
214 	const zio_t *z1 = (const zio_t *)x1;
215 	const zio_t *z2 = (const zio_t *)x2;
216 
217 	int cmp = TREE_CMP(z1->io_offset, z2->io_offset);
218 
219 	if (likely(cmp))
220 		return (cmp);
221 
222 	return (TREE_PCMP(z1, z2));
223 }
224 
225 static inline avl_tree_t *
vdev_queue_class_tree(vdev_queue_t * vq,zio_priority_t p)226 vdev_queue_class_tree(vdev_queue_t *vq, zio_priority_t p)
227 {
228 	return (&vq->vq_class[p].vqc_queued_tree);
229 }
230 
231 static inline avl_tree_t *
vdev_queue_type_tree(vdev_queue_t * vq,zio_type_t t)232 vdev_queue_type_tree(vdev_queue_t *vq, zio_type_t t)
233 {
234 	ASSERT(t == ZIO_TYPE_READ || t == ZIO_TYPE_WRITE || t == ZIO_TYPE_TRIM);
235 	if (t == ZIO_TYPE_READ)
236 		return (&vq->vq_read_offset_tree);
237 	else if (t == ZIO_TYPE_WRITE)
238 		return (&vq->vq_write_offset_tree);
239 	else
240 		return (&vq->vq_trim_offset_tree);
241 }
242 
243 int
vdev_queue_timestamp_compare(const void * x1,const void * x2)244 vdev_queue_timestamp_compare(const void *x1, const void *x2)
245 {
246 	const zio_t *z1 = (const zio_t *)x1;
247 	const zio_t *z2 = (const zio_t *)x2;
248 
249 	int cmp = TREE_CMP(z1->io_timestamp, z2->io_timestamp);
250 
251 	if (likely(cmp))
252 		return (cmp);
253 
254 	return (TREE_PCMP(z1, z2));
255 }
256 
257 void
vdev_queue_init(vdev_t * vd)258 vdev_queue_init(vdev_t *vd)
259 {
260 	vdev_queue_t *vq = &vd->vdev_queue;
261 
262 	mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
263 	vq->vq_vdev = vd;
264 
265 	avl_create(&vq->vq_active_tree, vdev_queue_offset_compare,
266 	    sizeof (zio_t), offsetof(struct zio, io_queue_node));
267 	avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_READ),
268 	    vdev_queue_offset_compare, sizeof (zio_t),
269 	    offsetof(struct zio, io_offset_node));
270 	avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE),
271 	    vdev_queue_offset_compare, sizeof (zio_t),
272 	    offsetof(struct zio, io_offset_node));
273 	avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_TRIM),
274 	    vdev_queue_offset_compare, sizeof (zio_t),
275 	    offsetof(struct zio, io_offset_node));
276 
277 	for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
278 		int (*compfn) (const void *, const void *);
279 
280 		/*
281 		 * The synchronous/trim i/o queues are dispatched in FIFO rather
282 		 * than LBA order. This provides more consistent latency for
283 		 * these i/os.
284 		 */
285 		if (p == ZIO_PRIORITY_SYNC_READ ||
286 		    p == ZIO_PRIORITY_SYNC_WRITE ||
287 		    p == ZIO_PRIORITY_TRIM) {
288 			compfn = vdev_queue_timestamp_compare;
289 		} else {
290 			compfn = vdev_queue_offset_compare;
291 		}
292 
293 		avl_create(vdev_queue_class_tree(vq, p), compfn,
294 		    sizeof (zio_t), offsetof(struct zio, io_queue_node));
295 	}
296 
297 	vq->vq_last_offset = 0;
298 }
299 
300 void
vdev_queue_fini(vdev_t * vd)301 vdev_queue_fini(vdev_t *vd)
302 {
303 	vdev_queue_t *vq = &vd->vdev_queue;
304 
305 	for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
306 		avl_destroy(vdev_queue_class_tree(vq, p));
307 	avl_destroy(&vq->vq_active_tree);
308 	avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_READ));
309 	avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE));
310 	avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_TRIM));
311 
312 	mutex_destroy(&vq->vq_lock);
313 }
314 
315 static void
vdev_queue_io_add(vdev_queue_t * vq,zio_t * zio)316 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
317 {
318 	spa_t *spa = zio->io_spa;
319 
320 	ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
321 	avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);
322 	avl_add(vdev_queue_type_tree(vq, zio->io_type), zio);
323 
324 	mutex_enter(&spa->spa_iokstat_lock);
325 	spa->spa_queue_stats[zio->io_priority].spa_queued++;
326 	if (spa->spa_iokstat != NULL)
327 		kstat_waitq_enter(spa->spa_iokstat->ks_data);
328 	mutex_exit(&spa->spa_iokstat_lock);
329 }
330 
331 static void
vdev_queue_io_remove(vdev_queue_t * vq,zio_t * zio)332 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
333 {
334 	spa_t *spa = zio->io_spa;
335 
336 	ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
337 	avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
338 	avl_remove(vdev_queue_type_tree(vq, zio->io_type), zio);
339 
340 	mutex_enter(&spa->spa_iokstat_lock);
341 	ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0);
342 	spa->spa_queue_stats[zio->io_priority].spa_queued--;
343 	if (spa->spa_iokstat != NULL)
344 		kstat_waitq_exit(spa->spa_iokstat->ks_data);
345 	mutex_exit(&spa->spa_iokstat_lock);
346 }
347 
348 static void
vdev_queue_pending_add(vdev_queue_t * vq,zio_t * zio)349 vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio)
350 {
351 	spa_t *spa = zio->io_spa;
352 	ASSERT(MUTEX_HELD(&vq->vq_lock));
353 	ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
354 	vq->vq_class[zio->io_priority].vqc_active++;
355 	avl_add(&vq->vq_active_tree, zio);
356 
357 	mutex_enter(&spa->spa_iokstat_lock);
358 	spa->spa_queue_stats[zio->io_priority].spa_active++;
359 	if (spa->spa_iokstat != NULL)
360 		kstat_runq_enter(spa->spa_iokstat->ks_data);
361 	mutex_exit(&spa->spa_iokstat_lock);
362 }
363 
364 static void
vdev_queue_pending_remove(vdev_queue_t * vq,zio_t * zio)365 vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio)
366 {
367 	spa_t *spa = zio->io_spa;
368 	ASSERT(MUTEX_HELD(&vq->vq_lock));
369 	ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
370 	vq->vq_class[zio->io_priority].vqc_active--;
371 	avl_remove(&vq->vq_active_tree, zio);
372 
373 	mutex_enter(&spa->spa_iokstat_lock);
374 	ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0);
375 	spa->spa_queue_stats[zio->io_priority].spa_active--;
376 	if (spa->spa_iokstat != NULL) {
377 		kstat_io_t *ksio = spa->spa_iokstat->ks_data;
378 
379 		kstat_runq_exit(spa->spa_iokstat->ks_data);
380 		if (zio->io_type == ZIO_TYPE_READ) {
381 			ksio->reads++;
382 			ksio->nread += zio->io_size;
383 		} else if (zio->io_type == ZIO_TYPE_WRITE) {
384 			ksio->writes++;
385 			ksio->nwritten += zio->io_size;
386 		}
387 	}
388 	mutex_exit(&spa->spa_iokstat_lock);
389 }
390 
391 static void
vdev_queue_agg_io_done(zio_t * aio)392 vdev_queue_agg_io_done(zio_t *aio)
393 {
394 	if (aio->io_type == ZIO_TYPE_READ) {
395 		zio_t *pio;
396 		zio_link_t *zl = NULL;
397 		while ((pio = zio_walk_parents(aio, &zl)) != NULL) {
398 			abd_copy_off(pio->io_abd, aio->io_abd,
399 			    0, pio->io_offset - aio->io_offset, pio->io_size);
400 		}
401 	}
402 
403 	abd_free(aio->io_abd);
404 }
405 
406 static int
vdev_queue_class_min_active(zio_priority_t p)407 vdev_queue_class_min_active(zio_priority_t p)
408 {
409 	switch (p) {
410 	case ZIO_PRIORITY_SYNC_READ:
411 		return (zfs_vdev_sync_read_min_active);
412 	case ZIO_PRIORITY_SYNC_WRITE:
413 		return (zfs_vdev_sync_write_min_active);
414 	case ZIO_PRIORITY_ASYNC_READ:
415 		return (zfs_vdev_async_read_min_active);
416 	case ZIO_PRIORITY_ASYNC_WRITE:
417 		return (zfs_vdev_async_write_min_active);
418 	case ZIO_PRIORITY_SCRUB:
419 		return (zfs_vdev_scrub_min_active);
420 	case ZIO_PRIORITY_REMOVAL:
421 		return (zfs_vdev_removal_min_active);
422 	case ZIO_PRIORITY_INITIALIZING:
423 		return (zfs_vdev_initializing_min_active);
424 	case ZIO_PRIORITY_TRIM:
425 		return (zfs_vdev_trim_min_active);
426 	default:
427 		panic("invalid priority %u", p);
428 	}
429 }
430 
431 static int
vdev_queue_max_async_writes(spa_t * spa)432 vdev_queue_max_async_writes(spa_t *spa)
433 {
434 	int writes;
435 	uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total;
436 	uint64_t min_bytes = zfs_dirty_data_max *
437 	    zfs_vdev_async_write_active_min_dirty_percent / 100;
438 	uint64_t max_bytes = zfs_dirty_data_max *
439 	    zfs_vdev_async_write_active_max_dirty_percent / 100;
440 
441 	/*
442 	 * Sync tasks correspond to interactive user actions. To reduce the
443 	 * execution time of those actions we push data out as fast as possible.
444 	 */
445 	if (spa_has_pending_synctask(spa)) {
446 		return (zfs_vdev_async_write_max_active);
447 	}
448 
449 	if (dirty < min_bytes)
450 		return (zfs_vdev_async_write_min_active);
451 	if (dirty > max_bytes)
452 		return (zfs_vdev_async_write_max_active);
453 
454 	/*
455 	 * linear interpolation:
456 	 * slope = (max_writes - min_writes) / (max_bytes - min_bytes)
457 	 * move right by min_bytes
458 	 * move up by min_writes
459 	 */
460 	writes = (dirty - min_bytes) *
461 	    (zfs_vdev_async_write_max_active -
462 	    zfs_vdev_async_write_min_active) /
463 	    (max_bytes - min_bytes) +
464 	    zfs_vdev_async_write_min_active;
465 	ASSERT3U(writes, >=, zfs_vdev_async_write_min_active);
466 	ASSERT3U(writes, <=, zfs_vdev_async_write_max_active);
467 	return (writes);
468 }
469 
470 static int
vdev_queue_class_max_active(spa_t * spa,zio_priority_t p)471 vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
472 {
473 	switch (p) {
474 	case ZIO_PRIORITY_SYNC_READ:
475 		return (zfs_vdev_sync_read_max_active);
476 	case ZIO_PRIORITY_SYNC_WRITE:
477 		return (zfs_vdev_sync_write_max_active);
478 	case ZIO_PRIORITY_ASYNC_READ:
479 		return (zfs_vdev_async_read_max_active);
480 	case ZIO_PRIORITY_ASYNC_WRITE:
481 		return (vdev_queue_max_async_writes(spa));
482 	case ZIO_PRIORITY_SCRUB:
483 		return (zfs_vdev_scrub_max_active);
484 	case ZIO_PRIORITY_REMOVAL:
485 		return (zfs_vdev_removal_max_active);
486 	case ZIO_PRIORITY_INITIALIZING:
487 		return (zfs_vdev_initializing_max_active);
488 	case ZIO_PRIORITY_TRIM:
489 		return (zfs_vdev_trim_max_active);
490 	default:
491 		panic("invalid priority %u", p);
492 	}
493 }
494 
495 /*
496  * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if
497  * there is no eligible class.
498  */
499 static zio_priority_t
vdev_queue_class_to_issue(vdev_queue_t * vq)500 vdev_queue_class_to_issue(vdev_queue_t *vq)
501 {
502 	spa_t *spa = vq->vq_vdev->vdev_spa;
503 	zio_priority_t p;
504 
505 	if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active)
506 		return (ZIO_PRIORITY_NUM_QUEUEABLE);
507 
508 	/* find a queue that has not reached its minimum # outstanding i/os */
509 	for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
510 		if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
511 		    vq->vq_class[p].vqc_active <
512 		    vdev_queue_class_min_active(p))
513 			return (p);
514 	}
515 
516 	/*
517 	 * If we haven't found a queue, look for one that hasn't reached its
518 	 * maximum # outstanding i/os.
519 	 */
520 	for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
521 		if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
522 		    vq->vq_class[p].vqc_active <
523 		    vdev_queue_class_max_active(spa, p))
524 			return (p);
525 	}
526 
527 	/* No eligible queued i/os */
528 	return (ZIO_PRIORITY_NUM_QUEUEABLE);
529 }
530 
531 /*
532  * Compute the range spanned by two i/os, which is the endpoint of the last
533  * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
534  * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
535  * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
536  */
537 #define	IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
538 #define	IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
539 
540 static zio_t *
vdev_queue_aggregate(vdev_queue_t * vq,zio_t * zio)541 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
542 {
543 	zio_t *first, *last, *aio, *dio, *mandatory, *nio;
544 	zio_link_t *zl = NULL;
545 	uint64_t maxgap = 0;
546 	uint64_t size;
547 	boolean_t stretch = B_FALSE;
548 	avl_tree_t *t = vdev_queue_type_tree(vq, zio->io_type);
549 	enum zio_flag flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT;
550 
551 	if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE)
552 		return (NULL);
553 
554 	/*
555 	 * While TRIM commands could be aggregated based on offset this
556 	 * behavior is disabled until it's determined to be beneficial.
557 	 */
558 	if (zio->io_type == ZIO_TYPE_TRIM && !zfs_vdev_aggregate_trim)
559 		return (NULL);
560 
561 	first = last = zio;
562 
563 	if (zio->io_type == ZIO_TYPE_READ)
564 		maxgap = zfs_vdev_read_gap_limit;
565 
566 	/*
567 	 * We can aggregate I/Os that are sufficiently adjacent and of
568 	 * the same flavor, as expressed by the AGG_INHERIT flags.
569 	 * The latter requirement is necessary so that certain
570 	 * attributes of the I/O, such as whether it's a normal I/O
571 	 * or a scrub/resilver, can be preserved in the aggregate.
572 	 * We can include optional I/Os, but don't allow them
573 	 * to begin a range as they add no benefit in that situation.
574 	 */
575 
576 	/*
577 	 * We keep track of the last non-optional I/O.
578 	 */
579 	mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first;
580 
581 	/*
582 	 * Walk backwards through sufficiently contiguous I/Os
583 	 * recording the last non-optional I/O.
584 	 */
585 	while ((dio = AVL_PREV(t, first)) != NULL &&
586 	    (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
587 	    IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit &&
588 	    IO_GAP(dio, first) <= maxgap &&
589 	    dio->io_type == zio->io_type) {
590 		first = dio;
591 		if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL))
592 			mandatory = first;
593 	}
594 
595 	/*
596 	 * Skip any initial optional I/Os.
597 	 */
598 	while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) {
599 		first = AVL_NEXT(t, first);
600 		ASSERT(first != NULL);
601 	}
602 
603 	/*
604 	 * Walk forward through sufficiently contiguous I/Os.
605 	 * The aggregation limit does not apply to optional i/os, so that
606 	 * we can issue contiguous writes even if they are larger than the
607 	 * aggregation limit.
608 	 */
609 	while ((dio = AVL_NEXT(t, last)) != NULL &&
610 	    (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
611 	    (IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit ||
612 	    (dio->io_flags & ZIO_FLAG_OPTIONAL)) &&
613 	    IO_GAP(last, dio) <= maxgap &&
614 	    dio->io_type == zio->io_type) {
615 		last = dio;
616 		if (!(last->io_flags & ZIO_FLAG_OPTIONAL))
617 			mandatory = last;
618 	}
619 
620 	/*
621 	 * Now that we've established the range of the I/O aggregation
622 	 * we must decide what to do with trailing optional I/Os.
623 	 * For reads, there's nothing to do. While we are unable to
624 	 * aggregate further, it's possible that a trailing optional
625 	 * I/O would allow the underlying device to aggregate with
626 	 * subsequent I/Os. We must therefore determine if the next
627 	 * non-optional I/O is close enough to make aggregation
628 	 * worthwhile.
629 	 */
630 	if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) {
631 		zio_t *nio = last;
632 		while ((dio = AVL_NEXT(t, nio)) != NULL &&
633 		    IO_GAP(nio, dio) == 0 &&
634 		    IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) {
635 			nio = dio;
636 			if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
637 				stretch = B_TRUE;
638 				break;
639 			}
640 		}
641 	}
642 
643 	if (stretch) {
644 		/*
645 		 * We are going to include an optional io in our aggregated
646 		 * span, thus closing the write gap.  Only mandatory i/os can
647 		 * start aggregated spans, so make sure that the next i/o
648 		 * after our span is mandatory.
649 		 */
650 		dio = AVL_NEXT(t, last);
651 		dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
652 	} else {
653 		/* do not include the optional i/o */
654 		while (last != mandatory && last != first) {
655 			ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL);
656 			last = AVL_PREV(t, last);
657 			ASSERT(last != NULL);
658 		}
659 	}
660 
661 	if (first == last)
662 		return (NULL);
663 
664 	size = IO_SPAN(first, last);
665 	ASSERT3U(size, <=, SPA_MAXBLOCKSIZE);
666 
667 	aio = zio_vdev_delegated_io(first->io_vd, first->io_offset,
668 	    abd_alloc_for_io(size, B_TRUE), size, first->io_type,
669 	    zio->io_priority, flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
670 	    vdev_queue_agg_io_done, NULL);
671 	aio->io_timestamp = first->io_timestamp;
672 
673 	nio = first;
674 	do {
675 		dio = nio;
676 		nio = AVL_NEXT(t, dio);
677 		ASSERT3U(dio->io_type, ==, aio->io_type);
678 
679 		if (dio->io_flags & ZIO_FLAG_NODATA) {
680 			ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE);
681 			abd_zero_off(aio->io_abd,
682 			    dio->io_offset - aio->io_offset, dio->io_size);
683 		} else if (dio->io_type == ZIO_TYPE_WRITE) {
684 			abd_copy_off(aio->io_abd, dio->io_abd,
685 			    dio->io_offset - aio->io_offset, 0, dio->io_size);
686 		}
687 
688 		zio_add_child(dio, aio);
689 		vdev_queue_io_remove(vq, dio);
690 	} while (dio != last);
691 
692 	/*
693 	 * We need to drop the vdev queue's lock to avoid a deadlock that we
694 	 * could encounter since this I/O will complete immediately.
695 	 */
696 	mutex_exit(&vq->vq_lock);
697 	while ((dio = zio_walk_parents(aio, &zl)) != NULL) {
698 		zio_vdev_io_bypass(dio);
699 		zio_execute(dio);
700 	}
701 	mutex_enter(&vq->vq_lock);
702 
703 	return (aio);
704 }
705 
706 static zio_t *
vdev_queue_io_to_issue(vdev_queue_t * vq)707 vdev_queue_io_to_issue(vdev_queue_t *vq)
708 {
709 	zio_t *zio, *aio;
710 	zio_priority_t p;
711 	avl_index_t idx;
712 	avl_tree_t *tree;
713 	zio_t search;
714 
715 again:
716 	ASSERT(MUTEX_HELD(&vq->vq_lock));
717 
718 	p = vdev_queue_class_to_issue(vq);
719 
720 	if (p == ZIO_PRIORITY_NUM_QUEUEABLE) {
721 		/* No eligible queued i/os */
722 		return (NULL);
723 	}
724 
725 	/*
726 	 * For LBA-ordered queues (async / scrub / initializing), issue the
727 	 * i/o which follows the most recently issued i/o in LBA (offset) order.
728 	 *
729 	 * For FIFO queues (sync/trim), issue the i/o with the lowest timestamp.
730 	 */
731 	tree = vdev_queue_class_tree(vq, p);
732 	search.io_timestamp = 0;
733 	search.io_offset = vq->vq_last_offset - 1;
734 	VERIFY3P(avl_find(tree, &search, &idx), ==, NULL);
735 	zio = avl_nearest(tree, idx, AVL_AFTER);
736 	if (zio == NULL)
737 		zio = avl_first(tree);
738 	ASSERT3U(zio->io_priority, ==, p);
739 
740 	aio = vdev_queue_aggregate(vq, zio);
741 	if (aio != NULL)
742 		zio = aio;
743 	else
744 		vdev_queue_io_remove(vq, zio);
745 
746 	/*
747 	 * If the I/O is or was optional and therefore has no data, we need to
748 	 * simply discard it. We need to drop the vdev queue's lock to avoid a
749 	 * deadlock that we could encounter since this I/O will complete
750 	 * immediately.
751 	 */
752 	if (zio->io_flags & ZIO_FLAG_NODATA) {
753 		mutex_exit(&vq->vq_lock);
754 		zio_vdev_io_bypass(zio);
755 		zio_execute(zio);
756 		mutex_enter(&vq->vq_lock);
757 		goto again;
758 	}
759 
760 	vdev_queue_pending_add(vq, zio);
761 	vq->vq_last_offset = zio->io_offset + zio->io_size;
762 
763 	return (zio);
764 }
765 
766 zio_t *
vdev_queue_io(zio_t * zio)767 vdev_queue_io(zio_t *zio)
768 {
769 	vdev_queue_t *vq = &zio->io_vd->vdev_queue;
770 	zio_t *nio;
771 
772 	if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
773 		return (zio);
774 
775 	/*
776 	 * Children i/os inherent their parent's priority, which might
777 	 * not match the child's i/o type.  Fix it up here.
778 	 */
779 	if (zio->io_type == ZIO_TYPE_READ) {
780 		ASSERT(zio->io_priority != ZIO_PRIORITY_TRIM);
781 
782 		if (zio->io_priority != ZIO_PRIORITY_SYNC_READ &&
783 		    zio->io_priority != ZIO_PRIORITY_ASYNC_READ &&
784 		    zio->io_priority != ZIO_PRIORITY_SCRUB &&
785 		    zio->io_priority != ZIO_PRIORITY_REMOVAL &&
786 		    zio->io_priority != ZIO_PRIORITY_INITIALIZING) {
787 			zio->io_priority = ZIO_PRIORITY_ASYNC_READ;
788 		}
789 	} else if (zio->io_type == ZIO_TYPE_WRITE) {
790 		ASSERT(zio->io_priority != ZIO_PRIORITY_TRIM);
791 
792 		if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE &&
793 		    zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE &&
794 		    zio->io_priority != ZIO_PRIORITY_REMOVAL &&
795 		    zio->io_priority != ZIO_PRIORITY_INITIALIZING) {
796 			zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE;
797 		}
798 	} else {
799 		ASSERT(zio->io_type == ZIO_TYPE_TRIM);
800 		ASSERT(zio->io_priority == ZIO_PRIORITY_TRIM);
801 	}
802 
803 	zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
804 
805 	mutex_enter(&vq->vq_lock);
806 	zio->io_timestamp = gethrtime();
807 	vdev_queue_io_add(vq, zio);
808 	nio = vdev_queue_io_to_issue(vq);
809 	mutex_exit(&vq->vq_lock);
810 
811 	if (nio == NULL)
812 		return (NULL);
813 
814 	if (nio->io_done == vdev_queue_agg_io_done) {
815 		zio_nowait(nio);
816 		return (NULL);
817 	}
818 
819 	return (nio);
820 }
821 
822 void
vdev_queue_io_done(zio_t * zio)823 vdev_queue_io_done(zio_t *zio)
824 {
825 	vdev_queue_t *vq = &zio->io_vd->vdev_queue;
826 	zio_t *nio;
827 
828 	mutex_enter(&vq->vq_lock);
829 
830 	vdev_queue_pending_remove(vq, zio);
831 
832 	zio->io_delta = gethrtime() - zio->io_timestamp;
833 	vq->vq_io_complete_ts = gethrtime();
834 
835 	while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
836 		mutex_exit(&vq->vq_lock);
837 		if (nio->io_done == vdev_queue_agg_io_done) {
838 			zio_nowait(nio);
839 		} else {
840 			zio_vdev_io_reissue(nio);
841 			zio_execute(nio);
842 		}
843 		mutex_enter(&vq->vq_lock);
844 	}
845 
846 	mutex_exit(&vq->vq_lock);
847 }
848 
849 void
vdev_queue_change_io_priority(zio_t * zio,zio_priority_t priority)850 vdev_queue_change_io_priority(zio_t *zio, zio_priority_t priority)
851 {
852 	vdev_queue_t *vq = &zio->io_vd->vdev_queue;
853 	avl_tree_t *tree;
854 
855 	/*
856 	 * ZIO_PRIORITY_NOW is used by the vdev cache code and the aggregate zio
857 	 * code to issue IOs without adding them to the vdev queue. In this
858 	 * case, the zio is already going to be issued as quickly as possible
859 	 * and so it doesn't need any reprioitization to help.
860 	 */
861 	if (zio->io_priority == ZIO_PRIORITY_NOW)
862 		return;
863 
864 	ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
865 	ASSERT3U(priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
866 
867 	if (zio->io_type == ZIO_TYPE_READ) {
868 		if (priority != ZIO_PRIORITY_SYNC_READ &&
869 		    priority != ZIO_PRIORITY_ASYNC_READ &&
870 		    priority != ZIO_PRIORITY_SCRUB)
871 			priority = ZIO_PRIORITY_ASYNC_READ;
872 	} else {
873 		ASSERT(zio->io_type == ZIO_TYPE_WRITE);
874 		if (priority != ZIO_PRIORITY_SYNC_WRITE &&
875 		    priority != ZIO_PRIORITY_ASYNC_WRITE)
876 			priority = ZIO_PRIORITY_ASYNC_WRITE;
877 	}
878 
879 	mutex_enter(&vq->vq_lock);
880 
881 	/*
882 	 * If the zio is in none of the queues we can simply change
883 	 * the priority. If the zio is waiting to be submitted we must
884 	 * remove it from the queue and re-insert it with the new priority.
885 	 * Otherwise, the zio is currently active and we cannot change its
886 	 * priority.
887 	 */
888 	tree = vdev_queue_class_tree(vq, zio->io_priority);
889 	if (avl_find(tree, zio, NULL) == zio) {
890 		spa_t *spa = zio->io_spa;
891 		zio_priority_t oldpri = zio->io_priority;
892 
893 		avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
894 		zio->io_priority = priority;
895 		avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);
896 
897 		mutex_enter(&spa->spa_iokstat_lock);
898 		ASSERT3U(spa->spa_queue_stats[oldpri].spa_queued, >, 0);
899 		spa->spa_queue_stats[oldpri].spa_queued--;
900 		spa->spa_queue_stats[zio->io_priority].spa_queued++;
901 		mutex_exit(&spa->spa_iokstat_lock);
902 	} else if (avl_find(&vq->vq_active_tree, zio, NULL) != zio) {
903 		zio->io_priority = priority;
904 	}
905 
906 	mutex_exit(&vq->vq_lock);
907 }
908 
909 /*
910  * As these two methods are only used for load calculations we're not
911  * concerned if we get an incorrect value on 32bit platforms due to lack of
912  * vq_lock mutex use here, instead we prefer to keep it lock free for
913  * performance.
914  */
915 int
vdev_queue_length(vdev_t * vd)916 vdev_queue_length(vdev_t *vd)
917 {
918 	return (avl_numnodes(&vd->vdev_queue.vq_active_tree));
919 }
920 
921 uint64_t
vdev_queue_last_offset(vdev_t * vd)922 vdev_queue_last_offset(vdev_t *vd)
923 {
924 	return (vd->vdev_queue.vq_last_offset);
925 }
926