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4045 zfs write throttle & i/o scheduler performance work
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
@@ -22,41 +22,142 @@
* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
#include <sys/vdev_impl.h>
#include <sys/spa_impl.h>
#include <sys/zio.h>
#include <sys/avl.h>
+#include <sys/dsl_pool.h>
/*
- * These tunables are for performance analysis.
+ * ZFS I/O Scheduler
+ * ---------------
+ *
+ * ZFS issues I/O operations to leaf vdevs to satisfy and complete zios. The
+ * I/O scheduler determines when and in what order those operations are
+ * issued. The I/O scheduler divides operations into five I/O classes
+ * prioritized in the following order: sync read, sync write, async read,
+ * async write, and scrub/resilver. Each queue defines the minimum and
+ * maximum number of concurrent operations that may be issued to the device.
+ * In addition, the device has an aggregate maximum. Note that the sum of the
+ * per-queue minimums must not exceed the aggregate maximum, and if the
+ * aggregate maximum is equal to or greater than the sum of the per-queue
+ * maximums, the per-queue minimum has no effect.
+ *
+ * For many physical devices, throughput increases with the number of
+ * concurrent operations, but latency typically suffers. Further, physical
+ * devices typically have a limit at which more concurrent operations have no
+ * effect on throughput or can actually cause it to decrease.
+ *
+ * The scheduler selects the next operation to issue by first looking for an
+ * I/O class whose minimum has not been satisfied. Once all are satisfied and
+ * the aggregate maximum has not been hit, the scheduler looks for classes
+ * whose maximum has not been satisfied. Iteration through the I/O classes is
+ * done in the order specified above. No further operations are issued if the
+ * aggregate maximum number of concurrent operations has been hit or if there
+ * are no operations queued for an I/O class that has not hit its maximum.
+ * Every time an i/o is queued or an operation completes, the I/O scheduler
+ * looks for new operations to issue.
+ *
+ * All I/O classes have a fixed maximum number of outstanding operations
+ * except for the async write class. Asynchronous writes represent the data
+ * that is committed to stable storage during the syncing stage for
+ * transaction groups (see txg.c). Transaction groups enter the syncing state
+ * periodically so the number of queued async writes will quickly burst up and
+ * then bleed down to zero. Rather than servicing them as quickly as possible,
+ * the I/O scheduler changes the maximum number of active async write i/os
+ * according to the amount of dirty data in the pool (see dsl_pool.c). Since
+ * both throughput and latency typically increase with the number of
+ * concurrent operations issued to physical devices, reducing the burstiness
+ * in the number of concurrent operations also stabilizes the response time of
+ * operations from other -- and in particular synchronous -- queues. In broad
+ * strokes, the I/O scheduler will issue more concurrent operations from the
+ * async write queue as there's more dirty data in the pool.
+ *
+ * Async Writes
+ *
+ * The number of concurrent operations issued for the async write I/O class
+ * follows a piece-wise linear function defined by a few adjustable points.
+ *
+ * | o---------| <-- zfs_vdev_async_write_max_active
+ * ^ | /^ |
+ * | | / | |
+ * active | / | |
+ * I/O | / | |
+ * count | / | |
+ * | / | |
+ * |------------o | | <-- zfs_vdev_async_write_min_active
+ * 0|____________^______|_________|
+ * 0% | | 100% of zfs_dirty_data_max
+ * | |
+ * | `-- zfs_vdev_async_write_active_max_dirty_percent
+ * `--------- zfs_vdev_async_write_active_min_dirty_percent
+ *
+ * Until the amount of dirty data exceeds a minimum percentage of the dirty
+ * data allowed in the pool, the I/O scheduler will limit the number of
+ * concurrent operations to the minimum. As that threshold is crossed, the
+ * number of concurrent operations issued increases linearly to the maximum at
+ * the specified maximum percentage of the dirty data allowed in the pool.
+ *
+ * Ideally, the amount of dirty data on a busy pool will stay in the sloped
+ * part of the function between zfs_vdev_async_write_active_min_dirty_percent
+ * and zfs_vdev_async_write_active_max_dirty_percent. If it exceeds the
+ * maximum percentage, this indicates that the rate of incoming data is
+ * greater than the rate that the backend storage can handle. In this case, we
+ * must further throttle incoming writes (see dmu_tx_delay() for details).
*/
-/* The maximum number of I/Os concurrently pending to each device. */
-int zfs_vdev_max_pending = 10;
+/*
+ * The maximum number of i/os active to each device. Ideally, this will be >=
+ * the sum of each queue's max_active. It must be at least the sum of each
+ * queue's min_active.
+ */
+uint32_t zfs_vdev_max_active = 1000;
/*
- * The initial number of I/Os pending to each device, before it starts ramping
- * up to zfs_vdev_max_pending.
+ * Per-queue limits on the number of i/os active to each device. If the
+ * sum of the queue's max_active is < zfs_vdev_max_active, then the
+ * min_active comes into play. We will send min_active from each queue,
+ * and then select from queues in the order defined by zio_priority_t.
+ *
+ * In general, smaller max_active's will lead to lower latency of synchronous
+ * operations. Larger max_active's may lead to higher overall throughput,
+ * depending on underlying storage.
+ *
+ * The ratio of the queues' max_actives determines the balance of performance
+ * between reads, writes, and scrubs. E.g., increasing
+ * zfs_vdev_scrub_max_active will cause the scrub or resilver to complete
+ * more quickly, but reads and writes to have higher latency and lower
+ * throughput.
*/
-int zfs_vdev_min_pending = 4;
+uint32_t zfs_vdev_sync_read_min_active = 10;
+uint32_t zfs_vdev_sync_read_max_active = 10;
+uint32_t zfs_vdev_sync_write_min_active = 10;
+uint32_t zfs_vdev_sync_write_max_active = 10;
+uint32_t zfs_vdev_async_read_min_active = 1;
+uint32_t zfs_vdev_async_read_max_active = 3;
+uint32_t zfs_vdev_async_write_min_active = 1;
+uint32_t zfs_vdev_async_write_max_active = 10;
+uint32_t zfs_vdev_scrub_min_active = 1;
+uint32_t zfs_vdev_scrub_max_active = 2;
/*
- * The deadlines are grouped into buckets based on zfs_vdev_time_shift:
- * deadline = pri + gethrtime() >> time_shift)
+ * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent
+ * dirty data, use zfs_vdev_async_write_min_active. When it has more than
+ * zfs_vdev_async_write_active_max_dirty_percent, use
+ * zfs_vdev_async_write_max_active. The value is linearly interpolated
+ * between min and max.
*/
-int zfs_vdev_time_shift = 29; /* each bucket is 0.537 seconds */
+int zfs_vdev_async_write_active_min_dirty_percent = 30;
+int zfs_vdev_async_write_active_max_dirty_percent = 60;
-/* exponential I/O issue ramp-up rate */
-int zfs_vdev_ramp_rate = 2;
-
/*
* To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
* For read I/Os, we also aggregate across small adjacency gaps; for writes
* we include spans of optional I/Os to aid aggregation at the disk even when
* they aren't able to help us aggregate at this level.
@@ -63,24 +164,16 @@
*/
int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE;
int zfs_vdev_read_gap_limit = 32 << 10;
int zfs_vdev_write_gap_limit = 4 << 10;
-/*
- * Virtual device vector for disk I/O scheduling.
- */
int
-vdev_queue_deadline_compare(const void *x1, const void *x2)
+vdev_queue_offset_compare(const void *x1, const void *x2)
{
const zio_t *z1 = x1;
const zio_t *z2 = x2;
- if (z1->io_deadline < z2->io_deadline)
- return (-1);
- if (z1->io_deadline > z2->io_deadline)
- return (1);
-
if (z1->io_offset < z2->io_offset)
return (-1);
if (z1->io_offset > z2->io_offset)
return (1);
@@ -91,18 +184,18 @@
return (0);
}
int
-vdev_queue_offset_compare(const void *x1, const void *x2)
+vdev_queue_timestamp_compare(const void *x1, const void *x2)
{
const zio_t *z1 = x1;
const zio_t *z2 = x2;
- if (z1->io_offset < z2->io_offset)
+ if (z1->io_timestamp < z2->io_timestamp)
return (-1);
- if (z1->io_offset > z2->io_offset)
+ if (z1->io_timestamp > z2->io_timestamp)
return (1);
if (z1 < z2)
return (-1);
if (z1 > z2)
@@ -115,144 +208,273 @@
vdev_queue_init(vdev_t *vd)
{
vdev_queue_t *vq = &vd->vdev_queue;
mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
+ vq->vq_vdev = vd;
- avl_create(&vq->vq_deadline_tree, vdev_queue_deadline_compare,
- sizeof (zio_t), offsetof(struct zio, io_deadline_node));
+ avl_create(&vq->vq_active_tree, vdev_queue_offset_compare,
+ sizeof (zio_t), offsetof(struct zio, io_queue_node));
- avl_create(&vq->vq_read_tree, vdev_queue_offset_compare,
- sizeof (zio_t), offsetof(struct zio, io_offset_node));
-
- avl_create(&vq->vq_write_tree, vdev_queue_offset_compare,
- sizeof (zio_t), offsetof(struct zio, io_offset_node));
-
- avl_create(&vq->vq_pending_tree, vdev_queue_offset_compare,
- sizeof (zio_t), offsetof(struct zio, io_offset_node));
+ for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
+ /*
+ * The synchronous i/o queues are FIFO rather than LBA ordered.
+ * This provides more consistent latency for these i/os, and
+ * they tend to not be tightly clustered anyway so there is
+ * little to no throughput loss.
+ */
+ boolean_t fifo = (p == ZIO_PRIORITY_SYNC_READ ||
+ p == ZIO_PRIORITY_SYNC_WRITE);
+ avl_create(&vq->vq_class[p].vqc_queued_tree,
+ fifo ? vdev_queue_timestamp_compare :
+ vdev_queue_offset_compare,
+ sizeof (zio_t), offsetof(struct zio, io_queue_node));
+ }
}
void
vdev_queue_fini(vdev_t *vd)
{
vdev_queue_t *vq = &vd->vdev_queue;
- avl_destroy(&vq->vq_deadline_tree);
- avl_destroy(&vq->vq_read_tree);
- avl_destroy(&vq->vq_write_tree);
- avl_destroy(&vq->vq_pending_tree);
+ for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
+ avl_destroy(&vq->vq_class[p].vqc_queued_tree);
+ avl_destroy(&vq->vq_active_tree);
mutex_destroy(&vq->vq_lock);
}
static void
vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
{
spa_t *spa = zio->io_spa;
- avl_add(&vq->vq_deadline_tree, zio);
- avl_add(zio->io_vdev_tree, zio);
+ ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
+ avl_add(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio);
- if (spa->spa_iokstat != NULL) {
mutex_enter(&spa->spa_iokstat_lock);
+ spa->spa_queue_stats[zio->io_priority].spa_queued++;
+ if (spa->spa_iokstat != NULL)
kstat_waitq_enter(spa->spa_iokstat->ks_data);
mutex_exit(&spa->spa_iokstat_lock);
- }
}
static void
vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
{
spa_t *spa = zio->io_spa;
- avl_remove(&vq->vq_deadline_tree, zio);
- avl_remove(zio->io_vdev_tree, zio);
+ ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
+ avl_remove(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio);
- if (spa->spa_iokstat != NULL) {
mutex_enter(&spa->spa_iokstat_lock);
+ ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0);
+ spa->spa_queue_stats[zio->io_priority].spa_queued--;
+ if (spa->spa_iokstat != NULL)
kstat_waitq_exit(spa->spa_iokstat->ks_data);
mutex_exit(&spa->spa_iokstat_lock);
- }
}
static void
vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio)
{
spa_t *spa = zio->io_spa;
- avl_add(&vq->vq_pending_tree, zio);
- if (spa->spa_iokstat != NULL) {
+ ASSERT(MUTEX_HELD(&vq->vq_lock));
+ ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
+ vq->vq_class[zio->io_priority].vqc_active++;
+ avl_add(&vq->vq_active_tree, zio);
+
mutex_enter(&spa->spa_iokstat_lock);
+ spa->spa_queue_stats[zio->io_priority].spa_active++;
+ if (spa->spa_iokstat != NULL)
kstat_runq_enter(spa->spa_iokstat->ks_data);
mutex_exit(&spa->spa_iokstat_lock);
- }
}
static void
vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio)
{
spa_t *spa = zio->io_spa;
- avl_remove(&vq->vq_pending_tree, zio);
+ ASSERT(MUTEX_HELD(&vq->vq_lock));
+ ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
+ vq->vq_class[zio->io_priority].vqc_active--;
+ avl_remove(&vq->vq_active_tree, zio);
+
+ mutex_enter(&spa->spa_iokstat_lock);
+ ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0);
+ spa->spa_queue_stats[zio->io_priority].spa_active--;
if (spa->spa_iokstat != NULL) {
kstat_io_t *ksio = spa->spa_iokstat->ks_data;
- mutex_enter(&spa->spa_iokstat_lock);
kstat_runq_exit(spa->spa_iokstat->ks_data);
if (zio->io_type == ZIO_TYPE_READ) {
ksio->reads++;
ksio->nread += zio->io_size;
} else if (zio->io_type == ZIO_TYPE_WRITE) {
ksio->writes++;
ksio->nwritten += zio->io_size;
}
- mutex_exit(&spa->spa_iokstat_lock);
}
+ mutex_exit(&spa->spa_iokstat_lock);
}
static void
vdev_queue_agg_io_done(zio_t *aio)
{
+ if (aio->io_type == ZIO_TYPE_READ) {
zio_t *pio;
-
- while ((pio = zio_walk_parents(aio)) != NULL)
- if (aio->io_type == ZIO_TYPE_READ)
+ while ((pio = zio_walk_parents(aio)) != NULL) {
bcopy((char *)aio->io_data + (pio->io_offset -
aio->io_offset), pio->io_data, pio->io_size);
+ }
+ }
zio_buf_free(aio->io_data, aio->io_size);
}
+static int
+vdev_queue_class_min_active(zio_priority_t p)
+{
+ switch (p) {
+ case ZIO_PRIORITY_SYNC_READ:
+ return (zfs_vdev_sync_read_min_active);
+ case ZIO_PRIORITY_SYNC_WRITE:
+ return (zfs_vdev_sync_write_min_active);
+ case ZIO_PRIORITY_ASYNC_READ:
+ return (zfs_vdev_async_read_min_active);
+ case ZIO_PRIORITY_ASYNC_WRITE:
+ return (zfs_vdev_async_write_min_active);
+ case ZIO_PRIORITY_SCRUB:
+ return (zfs_vdev_scrub_min_active);
+ default:
+ panic("invalid priority %u", p);
+ return (0);
+ }
+}
+
+static int
+vdev_queue_max_async_writes(uint64_t dirty)
+{
+ int writes;
+ uint64_t min_bytes = zfs_dirty_data_max *
+ zfs_vdev_async_write_active_min_dirty_percent / 100;
+ uint64_t max_bytes = zfs_dirty_data_max *
+ zfs_vdev_async_write_active_max_dirty_percent / 100;
+
+ if (dirty < min_bytes)
+ return (zfs_vdev_async_write_min_active);
+ if (dirty > max_bytes)
+ return (zfs_vdev_async_write_max_active);
+
+ /*
+ * linear interpolation:
+ * slope = (max_writes - min_writes) / (max_bytes - min_bytes)
+ * move right by min_bytes
+ * move up by min_writes
+ */
+ writes = (dirty - min_bytes) *
+ (zfs_vdev_async_write_max_active -
+ zfs_vdev_async_write_min_active) /
+ (max_bytes - min_bytes) +
+ zfs_vdev_async_write_min_active;
+ ASSERT3U(writes, >=, zfs_vdev_async_write_min_active);
+ ASSERT3U(writes, <=, zfs_vdev_async_write_max_active);
+ return (writes);
+}
+
+static int
+vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
+{
+ switch (p) {
+ case ZIO_PRIORITY_SYNC_READ:
+ return (zfs_vdev_sync_read_max_active);
+ case ZIO_PRIORITY_SYNC_WRITE:
+ return (zfs_vdev_sync_write_max_active);
+ case ZIO_PRIORITY_ASYNC_READ:
+ return (zfs_vdev_async_read_max_active);
+ case ZIO_PRIORITY_ASYNC_WRITE:
+ return (vdev_queue_max_async_writes(
+ spa->spa_dsl_pool->dp_dirty_total));
+ case ZIO_PRIORITY_SCRUB:
+ return (zfs_vdev_scrub_max_active);
+ default:
+ panic("invalid priority %u", p);
+ return (0);
+ }
+}
+
/*
+ * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if
+ * there is no eligible class.
+ */
+static zio_priority_t
+vdev_queue_class_to_issue(vdev_queue_t *vq)
+{
+ spa_t *spa = vq->vq_vdev->vdev_spa;
+ zio_priority_t p;
+
+ if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active)
+ return (ZIO_PRIORITY_NUM_QUEUEABLE);
+
+ /* find a queue that has not reached its minimum # outstanding i/os */
+ for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
+ if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 &&
+ vq->vq_class[p].vqc_active <
+ vdev_queue_class_min_active(p))
+ return (p);
+ }
+
+ /*
+ * If we haven't found a queue, look for one that hasn't reached its
+ * maximum # outstanding i/os.
+ */
+ for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
+ if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 &&
+ vq->vq_class[p].vqc_active <
+ vdev_queue_class_max_active(spa, p))
+ return (p);
+ }
+
+ /* No eligible queued i/os */
+ return (ZIO_PRIORITY_NUM_QUEUEABLE);
+}
+
+/*
* Compute the range spanned by two i/os, which is the endpoint of the last
* (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
* Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
* thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
*/
#define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
#define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
static zio_t *
-vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
+vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
{
- zio_t *fio, *lio, *aio, *dio, *nio, *mio;
- avl_tree_t *t;
- int flags;
- uint64_t maxspan = zfs_vdev_aggregation_limit;
- uint64_t maxgap;
- int stretch;
+ zio_t *first, *last, *aio, *dio, *mandatory, *nio;
+ uint64_t maxgap = 0;
+ uint64_t size;
+ boolean_t stretch = B_FALSE;
+ vdev_queue_class_t *vqc = &vq->vq_class[zio->io_priority];
+ avl_tree_t *t = &vqc->vqc_queued_tree;
+ enum zio_flag flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT;
-again:
- ASSERT(MUTEX_HELD(&vq->vq_lock));
+ if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE)
+ return (NULL);
- if (avl_numnodes(&vq->vq_pending_tree) >= pending_limit ||
- avl_numnodes(&vq->vq_deadline_tree) == 0)
+ /*
+ * The synchronous i/o queues are not sorted by LBA, so we can't
+ * find adjacent i/os. These i/os tend to not be tightly clustered,
+ * or too large to aggregate, so this has little impact on performance.
+ */
+ if (zio->io_priority == ZIO_PRIORITY_SYNC_READ ||
+ zio->io_priority == ZIO_PRIORITY_SYNC_WRITE)
return (NULL);
- fio = lio = avl_first(&vq->vq_deadline_tree);
+ first = last = zio;
- t = fio->io_vdev_tree;
- flags = fio->io_flags & ZIO_FLAG_AGG_INHERIT;
- maxgap = (t == &vq->vq_read_tree) ? zfs_vdev_read_gap_limit : 0;
+ if (zio->io_type == ZIO_TYPE_READ)
+ maxgap = zfs_vdev_read_gap_limit;
- if (!(flags & ZIO_FLAG_DONT_AGGREGATE)) {
/*
* We can aggregate I/Os that are sufficiently adjacent and of
* the same flavor, as expressed by the AGG_INHERIT flags.
* The latter requirement is necessary so that certain
* attributes of the I/O, such as whether it's a normal I/O
@@ -262,43 +484,43 @@
*/
/*
* We keep track of the last non-optional I/O.
*/
- mio = (fio->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : fio;
+ mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first;
/*
* Walk backwards through sufficiently contiguous I/Os
* recording the last non-option I/O.
*/
- while ((dio = AVL_PREV(t, fio)) != NULL &&
+ while ((dio = AVL_PREV(t, first)) != NULL &&
(dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
- IO_SPAN(dio, lio) <= maxspan &&
- IO_GAP(dio, fio) <= maxgap) {
- fio = dio;
- if (mio == NULL && !(fio->io_flags & ZIO_FLAG_OPTIONAL))
- mio = fio;
+ IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit &&
+ IO_GAP(dio, first) <= maxgap) {
+ first = dio;
+ if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL))
+ mandatory = first;
}
/*
* Skip any initial optional I/Os.
*/
- while ((fio->io_flags & ZIO_FLAG_OPTIONAL) && fio != lio) {
- fio = AVL_NEXT(t, fio);
- ASSERT(fio != NULL);
+ while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) {
+ first = AVL_NEXT(t, first);
+ ASSERT(first != NULL);
}
/*
* Walk forward through sufficiently contiguous I/Os.
*/
- while ((dio = AVL_NEXT(t, lio)) != NULL &&
+ while ((dio = AVL_NEXT(t, last)) != NULL &&
(dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
- IO_SPAN(fio, dio) <= maxspan &&
- IO_GAP(lio, dio) <= maxgap) {
- lio = dio;
- if (!(lio->io_flags & ZIO_FLAG_OPTIONAL))
- mio = lio;
+ IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit &&
+ IO_GAP(last, dio) <= maxgap) {
+ last = dio;
+ if (!(last->io_flags & ZIO_FLAG_OPTIONAL))
+ mandatory = last;
}
/*
* Now that we've established the range of the I/O aggregation
* we must decide what to do with trailing optional I/Os.
@@ -307,16 +529,15 @@
* I/O would allow the underlying device to aggregate with
* subsequent I/Os. We must therefore determine if the next
* non-optional I/O is close enough to make aggregation
* worthwhile.
*/
- stretch = B_FALSE;
- if (t != &vq->vq_read_tree && mio != NULL) {
- nio = lio;
+ if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) {
+ zio_t *nio = last;
while ((dio = AVL_NEXT(t, nio)) != NULL &&
IO_GAP(nio, dio) == 0 &&
- IO_GAP(mio, dio) <= zfs_vdev_write_gap_limit) {
+ IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) {
nio = dio;
if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
stretch = B_TRUE;
break;
}
@@ -323,40 +544,40 @@
}
}
if (stretch) {
/* This may be a no-op. */
- VERIFY((dio = AVL_NEXT(t, lio)) != NULL);
+ dio = AVL_NEXT(t, last);
dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
} else {
- while (lio != mio && lio != fio) {
- ASSERT(lio->io_flags & ZIO_FLAG_OPTIONAL);
- lio = AVL_PREV(t, lio);
- ASSERT(lio != NULL);
+ while (last != mandatory && last != first) {
+ ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL);
+ last = AVL_PREV(t, last);
+ ASSERT(last != NULL);
}
}
- }
- if (fio != lio) {
- uint64_t size = IO_SPAN(fio, lio);
- ASSERT(size <= zfs_vdev_aggregation_limit);
+ if (first == last)
+ return (NULL);
- aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset,
- zio_buf_alloc(size), size, fio->io_type, ZIO_PRIORITY_AGG,
+ size = IO_SPAN(first, last);
+ ASSERT3U(size, <=, zfs_vdev_aggregation_limit);
+
+ aio = zio_vdev_delegated_io(first->io_vd, first->io_offset,
+ zio_buf_alloc(size), size, first->io_type, zio->io_priority,
flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
vdev_queue_agg_io_done, NULL);
- aio->io_timestamp = fio->io_timestamp;
+ aio->io_timestamp = first->io_timestamp;
- nio = fio;
+ nio = first;
do {
dio = nio;
nio = AVL_NEXT(t, dio);
- ASSERT(dio->io_type == aio->io_type);
- ASSERT(dio->io_vdev_tree == t);
+ ASSERT3U(dio->io_type, ==, aio->io_type);
if (dio->io_flags & ZIO_FLAG_NODATA) {
- ASSERT(dio->io_type == ZIO_TYPE_WRITE);
+ ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE);
bzero((char *)aio->io_data + (dio->io_offset -
aio->io_offset), dio->io_size);
} else if (dio->io_type == ZIO_TYPE_WRITE) {
bcopy(dio->io_data, (char *)aio->io_data +
(dio->io_offset - aio->io_offset),
@@ -365,67 +586,106 @@
zio_add_child(dio, aio);
vdev_queue_io_remove(vq, dio);
zio_vdev_io_bypass(dio);
zio_execute(dio);
- } while (dio != lio);
+ } while (dio != last);
- vdev_queue_pending_add(vq, aio);
-
return (aio);
+}
+
+static zio_t *
+vdev_queue_io_to_issue(vdev_queue_t *vq)
+{
+ zio_t *zio, *aio;
+ zio_priority_t p;
+ avl_index_t idx;
+ vdev_queue_class_t *vqc;
+ zio_t search;
+
+again:
+ ASSERT(MUTEX_HELD(&vq->vq_lock));
+
+ p = vdev_queue_class_to_issue(vq);
+
+ if (p == ZIO_PRIORITY_NUM_QUEUEABLE) {
+ /* No eligible queued i/os */
+ return (NULL);
}
- ASSERT(fio->io_vdev_tree == t);
- vdev_queue_io_remove(vq, fio);
+ /*
+ * For LBA-ordered queues (async / scrub), issue the i/o which follows
+ * the most recently issued i/o in LBA (offset) order.
+ *
+ * For FIFO queues (sync), issue the i/o with the lowest timestamp.
+ */
+ vqc = &vq->vq_class[p];
+ search.io_timestamp = 0;
+ search.io_offset = vq->vq_last_offset + 1;
+ VERIFY3P(avl_find(&vqc->vqc_queued_tree, &search, &idx), ==, NULL);
+ zio = avl_nearest(&vqc->vqc_queued_tree, idx, AVL_AFTER);
+ if (zio == NULL)
+ zio = avl_first(&vqc->vqc_queued_tree);
+ ASSERT3U(zio->io_priority, ==, p);
+ aio = vdev_queue_aggregate(vq, zio);
+ if (aio != NULL)
+ zio = aio;
+ else
+ vdev_queue_io_remove(vq, zio);
+
/*
* If the I/O is or was optional and therefore has no data, we need to
* simply discard it. We need to drop the vdev queue's lock to avoid a
* deadlock that we could encounter since this I/O will complete
* immediately.
*/
- if (fio->io_flags & ZIO_FLAG_NODATA) {
+ if (zio->io_flags & ZIO_FLAG_NODATA) {
mutex_exit(&vq->vq_lock);
- zio_vdev_io_bypass(fio);
- zio_execute(fio);
+ zio_vdev_io_bypass(zio);
+ zio_execute(zio);
mutex_enter(&vq->vq_lock);
goto again;
}
- vdev_queue_pending_add(vq, fio);
+ vdev_queue_pending_add(vq, zio);
+ vq->vq_last_offset = zio->io_offset;
- return (fio);
+ return (zio);
}
zio_t *
vdev_queue_io(zio_t *zio)
{
vdev_queue_t *vq = &zio->io_vd->vdev_queue;
zio_t *nio;
- ASSERT(zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE);
-
if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
return (zio);
+ /*
+ * Children i/os inherent their parent's priority, which might
+ * not match the child's i/o type. Fix it up here.
+ */
+ if (zio->io_type == ZIO_TYPE_READ) {
+ if (zio->io_priority != ZIO_PRIORITY_SYNC_READ &&
+ zio->io_priority != ZIO_PRIORITY_ASYNC_READ &&
+ zio->io_priority != ZIO_PRIORITY_SCRUB)
+ zio->io_priority = ZIO_PRIORITY_ASYNC_READ;
+ } else {
+ ASSERT(zio->io_type == ZIO_TYPE_WRITE);
+ if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE &&
+ zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE)
+ zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE;
+ }
+
zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
- if (zio->io_type == ZIO_TYPE_READ)
- zio->io_vdev_tree = &vq->vq_read_tree;
- else
- zio->io_vdev_tree = &vq->vq_write_tree;
-
mutex_enter(&vq->vq_lock);
-
zio->io_timestamp = gethrtime();
- zio->io_deadline = (zio->io_timestamp >> zfs_vdev_time_shift) +
- zio->io_priority;
-
vdev_queue_io_add(vq, zio);
-
- nio = vdev_queue_io_to_issue(vq, zfs_vdev_min_pending);
-
+ nio = vdev_queue_io_to_issue(vq);
mutex_exit(&vq->vq_lock);
if (nio == NULL)
return (NULL);
@@ -439,10 +699,11 @@
void
vdev_queue_io_done(zio_t *zio)
{
vdev_queue_t *vq = &zio->io_vd->vdev_queue;
+ zio_t *nio;
if (zio_injection_enabled)
delay(SEC_TO_TICK(zio_handle_io_delay(zio)));
mutex_enter(&vq->vq_lock);
@@ -449,14 +710,11 @@
vdev_queue_pending_remove(vq, zio);
vq->vq_io_complete_ts = gethrtime();
- for (int i = 0; i < zfs_vdev_ramp_rate; i++) {
- zio_t *nio = vdev_queue_io_to_issue(vq, zfs_vdev_max_pending);
- if (nio == NULL)
- break;
+ while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
mutex_exit(&vq->vq_lock);
if (nio->io_done == vdev_queue_agg_io_done) {
zio_nowait(nio);
} else {
zio_vdev_io_reissue(nio);