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-rw-r--r--uts/common/fs/zfs/vdev_queue.c406
1 files changed, 406 insertions, 0 deletions
diff --git a/uts/common/fs/zfs/vdev_queue.c b/uts/common/fs/zfs/vdev_queue.c
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index 000000000000..5a0d3ee97029
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+++ b/uts/common/fs/zfs/vdev_queue.c
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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/vdev_impl.h>
+#include <sys/zio.h>
+#include <sys/avl.h>
+
+/*
+ * These tunables are for performance analysis.
+ */
+/*
+ * zfs_vdev_max_pending is the maximum number of i/os concurrently
+ * pending to each device. zfs_vdev_min_pending is the initial number
+ * of i/os pending to each device (before it starts ramping up to
+ * max_pending).
+ */
+int zfs_vdev_max_pending = 10;
+int zfs_vdev_min_pending = 4;
+
+/* deadline = pri + ddi_get_lbolt64() >> time_shift) */
+int zfs_vdev_time_shift = 6;
+
+/* 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.
+ */
+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)
+{
+ 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);
+
+ if (z1 < z2)
+ return (-1);
+ if (z1 > z2)
+ return (1);
+
+ return (0);
+}
+
+int
+vdev_queue_offset_compare(const void *x1, const void *x2)
+{
+ const zio_t *z1 = x1;
+ const zio_t *z2 = x2;
+
+ if (z1->io_offset < z2->io_offset)
+ return (-1);
+ if (z1->io_offset > z2->io_offset)
+ return (1);
+
+ if (z1 < z2)
+ return (-1);
+ if (z1 > z2)
+ return (1);
+
+ return (0);
+}
+
+void
+vdev_queue_init(vdev_t *vd)
+{
+ vdev_queue_t *vq = &vd->vdev_queue;
+
+ mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
+
+ avl_create(&vq->vq_deadline_tree, vdev_queue_deadline_compare,
+ sizeof (zio_t), offsetof(struct zio, io_deadline_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));
+}
+
+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);
+
+ mutex_destroy(&vq->vq_lock);
+}
+
+static void
+vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
+{
+ avl_add(&vq->vq_deadline_tree, zio);
+ avl_add(zio->io_vdev_tree, zio);
+}
+
+static void
+vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
+{
+ avl_remove(&vq->vq_deadline_tree, zio);
+ avl_remove(zio->io_vdev_tree, zio);
+}
+
+static void
+vdev_queue_agg_io_done(zio_t *aio)
+{
+ zio_t *pio;
+
+ while ((pio = zio_walk_parents(aio)) != NULL)
+ if (aio->io_type == ZIO_TYPE_READ)
+ 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);
+}
+
+/*
+ * 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)
+{
+ 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;
+
+again:
+ ASSERT(MUTEX_HELD(&vq->vq_lock));
+
+ if (avl_numnodes(&vq->vq_pending_tree) >= pending_limit ||
+ avl_numnodes(&vq->vq_deadline_tree) == 0)
+ return (NULL);
+
+ fio = lio = avl_first(&vq->vq_deadline_tree);
+
+ 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 (!(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
+ * or a scrub/resilver, can be preserved in the aggregate.
+ * We can include optional I/Os, but don't allow them
+ * to begin a range as they add no benefit in that situation.
+ */
+
+ /*
+ * We keep track of the last non-optional I/O.
+ */
+ mio = (fio->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : fio;
+
+ /*
+ * Walk backwards through sufficiently contiguous I/Os
+ * recording the last non-option I/O.
+ */
+ while ((dio = AVL_PREV(t, fio)) != 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;
+ }
+
+ /*
+ * Skip any initial optional I/Os.
+ */
+ while ((fio->io_flags & ZIO_FLAG_OPTIONAL) && fio != lio) {
+ fio = AVL_NEXT(t, fio);
+ ASSERT(fio != NULL);
+ }
+
+ /*
+ * Walk forward through sufficiently contiguous I/Os.
+ */
+ while ((dio = AVL_NEXT(t, lio)) != 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;
+ }
+
+ /*
+ * Now that we've established the range of the I/O aggregation
+ * we must decide what to do with trailing optional I/Os.
+ * For reads, there's nothing to do. While we are unable to
+ * aggregate further, it's possible that a trailing optional
+ * 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;
+ while ((dio = AVL_NEXT(t, nio)) != NULL &&
+ IO_GAP(nio, dio) == 0 &&
+ IO_GAP(mio, dio) <= zfs_vdev_write_gap_limit) {
+ nio = dio;
+ if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
+ stretch = B_TRUE;
+ break;
+ }
+ }
+ }
+
+ if (stretch) {
+ /* This may be a no-op. */
+ VERIFY((dio = AVL_NEXT(t, lio)) != NULL);
+ 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);
+ }
+ }
+ }
+
+ if (fio != lio) {
+ uint64_t size = IO_SPAN(fio, lio);
+ ASSERT(size <= zfs_vdev_aggregation_limit);
+
+ aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset,
+ zio_buf_alloc(size), size, fio->io_type, ZIO_PRIORITY_AGG,
+ flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
+ vdev_queue_agg_io_done, NULL);
+
+ nio = fio;
+ do {
+ dio = nio;
+ nio = AVL_NEXT(t, dio);
+ ASSERT(dio->io_type == aio->io_type);
+ ASSERT(dio->io_vdev_tree == t);
+
+ if (dio->io_flags & ZIO_FLAG_NODATA) {
+ ASSERT(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),
+ dio->io_size);
+ }
+
+ zio_add_child(dio, aio);
+ vdev_queue_io_remove(vq, dio);
+ zio_vdev_io_bypass(dio);
+ zio_execute(dio);
+ } while (dio != lio);
+
+ avl_add(&vq->vq_pending_tree, aio);
+
+ return (aio);
+ }
+
+ ASSERT(fio->io_vdev_tree == t);
+ vdev_queue_io_remove(vq, fio);
+
+ /*
+ * 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) {
+ mutex_exit(&vq->vq_lock);
+ zio_vdev_io_bypass(fio);
+ zio_execute(fio);
+ mutex_enter(&vq->vq_lock);
+ goto again;
+ }
+
+ avl_add(&vq->vq_pending_tree, fio);
+
+ return (fio);
+}
+
+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);
+
+ 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_deadline = (ddi_get_lbolt64() >> zfs_vdev_time_shift) +
+ zio->io_priority;
+
+ vdev_queue_io_add(vq, zio);
+
+ nio = vdev_queue_io_to_issue(vq, zfs_vdev_min_pending);
+
+ mutex_exit(&vq->vq_lock);
+
+ if (nio == NULL)
+ return (NULL);
+
+ if (nio->io_done == vdev_queue_agg_io_done) {
+ zio_nowait(nio);
+ return (NULL);
+ }
+
+ return (nio);
+}
+
+void
+vdev_queue_io_done(zio_t *zio)
+{
+ vdev_queue_t *vq = &zio->io_vd->vdev_queue;
+
+ mutex_enter(&vq->vq_lock);
+
+ avl_remove(&vq->vq_pending_tree, zio);
+
+ 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;
+ mutex_exit(&vq->vq_lock);
+ if (nio->io_done == vdev_queue_agg_io_done) {
+ zio_nowait(nio);
+ } else {
+ zio_vdev_io_reissue(nio);
+ zio_execute(nio);
+ }
+ mutex_enter(&vq->vq_lock);
+ }
+
+ mutex_exit(&vq->vq_lock);
+}