freebsd-nq/module/zfs/vdev_mirror.c
smh 9f500936c8 FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information.
The existing algorithm selects a preferred leaf vdev based on offset of the zio
request modulo the number of members in the mirror. It assumes the devices are
of equal performance and that spreading the requests randomly over both drives
will be sufficient to saturate them. In practice this results in the leaf vdevs
being under utilized.

The new algorithm takes into the following additional factors:
* Load of the vdevs (number outstanding I/O requests)
* The locality of last queued I/O vs the new I/O request.

Within the locality calculation additional knowledge about the underlying vdev
is considered such as; is the device backing the vdev a rotating media device.

This results in performance increases across the board as well as significant
increases for predominantly streaming loads and for configurations which don't
have evenly performing devices.

The following are results from a setup with 3 Way Mirror with 2 x HD's and
1 x SSD from a basic test running multiple parrallel dd's.

With pre-fetch disabled (vfs.zfs.prefetch_disable=1):

== Stripe Balanced (default) ==
Read 15360MB using bs: 1048576, readers: 3, took 161 seconds @ 95 MB/s
== Load Balanced (zfslinux) ==
Read 15360MB using bs: 1048576, readers: 3, took 297 seconds @ 51 MB/s
== Load Balanced (locality freebsd) ==
Read 15360MB using bs: 1048576, readers: 3, took 54 seconds @ 284 MB/s

With pre-fetch enabled (vfs.zfs.prefetch_disable=0):

== Stripe Balanced (default) ==
Read 15360MB using bs: 1048576, readers: 3, took 91 seconds @ 168 MB/s
== Load Balanced (zfslinux) ==
Read 15360MB using bs: 1048576, readers: 3, took 108 seconds @ 142 MB/s
== Load Balanced (locality freebsd) ==
Read 15360MB using bs: 1048576, readers: 3, took 48 seconds @ 320 MB/s

In addition to the performance changes the code was also restructured, with
the help of Justin Gibbs, to provide a more logical flow which also ensures
vdevs loads are only calculated from the set of valid candidates.

The following additional sysctls where added to allow the administrator
to tune the behaviour of the load algorithm:
* vfs.zfs.vdev.mirror.rotating_inc
* vfs.zfs.vdev.mirror.rotating_seek_inc
* vfs.zfs.vdev.mirror.rotating_seek_offset
* vfs.zfs.vdev.mirror.non_rotating_inc
* vfs.zfs.vdev.mirror.non_rotating_seek_inc

These changes where based on work started by the zfsonlinux developers:
https://github.com/zfsonlinux/zfs/pull/1487

Reviewed by:	gibbs, mav, will
MFC after:	2 weeks
Sponsored by:	Multiplay

References:
  https://github.com/freebsd/freebsd@5c7a6f5d
  https://github.com/freebsd/freebsd@31b7f68d
  https://github.com/freebsd/freebsd@e186f564

Performance Testing:
  https://github.com/zfsonlinux/zfs/pull/4334#issuecomment-189057141

Porting notes:
- The tunables were adjusted to have ZoL-style names.
- The code was modified to use ZoL's vd_nonrot.
- Fixes were done to make cstyle.pl happy
- Merge conflicts were handled manually
- freebsd/freebsd@e186f564bc by my
  collegue Andriy Gapon has been included. It applied perfectly, but
  added a cstyle regression.
- This replaces 556011dbec entirely.
- A typo "IO'a" has been corrected to say "IO's"
- Descriptions of new tunables were added to man/man5/zfs-module-parameters.5.

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4334
2016-02-26 11:24:35 -08:00

668 lines
17 KiB
C

/*
* 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 2010 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* Copyright (c) 2012, 2014 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/vdev_impl.h>
#include <sys/zio.h>
#include <sys/fs/zfs.h>
/*
* Virtual device vector for mirroring.
*/
typedef struct mirror_child {
vdev_t *mc_vd;
uint64_t mc_offset;
int mc_error;
int mc_load;
uint8_t mc_tried;
uint8_t mc_skipped;
uint8_t mc_speculative;
} mirror_child_t;
typedef struct mirror_map {
int *mm_preferred;
int mm_preferred_cnt;
int mm_children;
boolean_t mm_replacing;
boolean_t mm_root;
mirror_child_t mm_child[];
} mirror_map_t;
static int vdev_mirror_shift = 21;
/*
* The load configuration settings below are tuned by default for
* the case where all devices are of the same rotational type.
*
* If there is a mixture of rotating and non-rotating media, setting
* zfs_vdev_mirror_non_rotating_seek_inc to 0 may well provide better results
* as it will direct more reads to the non-rotating vdevs which are more likely
* to have a higher performance.
*/
/* Rotating media load calculation configuration. */
static int zfs_vdev_mirror_rotating_inc = 0;
static int zfs_vdev_mirror_rotating_seek_inc = 5;
static int zfs_vdev_mirror_rotating_seek_offset = 1 * 1024 * 1024;
/* Non-rotating media load calculation configuration. */
static int zfs_vdev_mirror_non_rotating_inc = 0;
static int zfs_vdev_mirror_non_rotating_seek_inc = 1;
static inline size_t
vdev_mirror_map_size(int children)
{
return (offsetof(mirror_map_t, mm_child[children]) +
sizeof (int) * children);
}
static inline mirror_map_t *
vdev_mirror_map_alloc(int children, boolean_t replacing, boolean_t root)
{
mirror_map_t *mm;
mm = kmem_zalloc(vdev_mirror_map_size(children), KM_SLEEP);
mm->mm_children = children;
mm->mm_replacing = replacing;
mm->mm_root = root;
mm->mm_preferred = (int *)((uintptr_t)mm +
offsetof(mirror_map_t, mm_child[children]));
return (mm);
}
static void
vdev_mirror_map_free(zio_t *zio)
{
mirror_map_t *mm = zio->io_vsd;
kmem_free(mm, vdev_mirror_map_size(mm->mm_children));
}
static const zio_vsd_ops_t vdev_mirror_vsd_ops = {
vdev_mirror_map_free,
zio_vsd_default_cksum_report
};
static int
vdev_mirror_load(mirror_map_t *mm, vdev_t *vd, uint64_t zio_offset)
{
uint64_t lastoffset;
int load;
/* All DVAs have equal weight at the root. */
if (mm->mm_root)
return (INT_MAX);
/*
* We don't return INT_MAX if the device is resilvering i.e.
* vdev_resilver_txg != 0 as when tested performance was slightly
* worse overall when resilvering with compared to without.
*/
/* Standard load based on pending queue length. */
load = vdev_queue_length(vd);
lastoffset = vdev_queue_lastoffset(vd);
if (vd->vdev_nonrot) {
/* Non-rotating media. */
if (lastoffset == zio_offset)
return (load + zfs_vdev_mirror_non_rotating_inc);
/*
* Apply a seek penalty even for non-rotating devices as
* sequential I/O's can be aggregated into fewer operations on
* the device, thus avoiding unnecessary per-command overhead
* and boosting performance.
*/
return (load + zfs_vdev_mirror_non_rotating_seek_inc);
}
/* Rotating media I/O's which directly follow the last I/O. */
if (lastoffset == zio_offset)
return (load + zfs_vdev_mirror_rotating_inc);
/*
* Apply half the seek increment to I/O's within seek offset
* of the last I/O queued to this vdev as they should incure less
* of a seek increment.
*/
if (ABS(lastoffset - zio_offset) <
zfs_vdev_mirror_rotating_seek_offset)
return (load + (zfs_vdev_mirror_rotating_seek_inc / 2));
/* Apply the full seek increment to all other I/O's. */
return (load + zfs_vdev_mirror_rotating_seek_inc);
}
/*
* Avoid inlining the function to keep vdev_mirror_io_start(), which
* is this functions only caller, as small as possible on the stack.
*/
noinline static mirror_map_t *
vdev_mirror_map_init(zio_t *zio)
{
mirror_map_t *mm = NULL;
mirror_child_t *mc;
vdev_t *vd = zio->io_vd;
int c;
if (vd == NULL) {
dva_t *dva = zio->io_bp->blk_dva;
spa_t *spa = zio->io_spa;
mm = vdev_mirror_map_alloc(BP_GET_NDVAS(zio->io_bp), B_FALSE,
B_TRUE);
for (c = 0; c < mm->mm_children; c++) {
mc = &mm->mm_child[c];
mc->mc_vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[c]));
mc->mc_offset = DVA_GET_OFFSET(&dva[c]);
}
} else {
mm = vdev_mirror_map_alloc(vd->vdev_children,
(vd->vdev_ops == &vdev_replacing_ops ||
vd->vdev_ops == &vdev_spare_ops), B_FALSE);
for (c = 0; c < mm->mm_children; c++) {
mc = &mm->mm_child[c];
mc->mc_vd = vd->vdev_child[c];
mc->mc_offset = zio->io_offset;
}
}
zio->io_vsd = mm;
zio->io_vsd_ops = &vdev_mirror_vsd_ops;
return (mm);
}
static int
vdev_mirror_open(vdev_t *vd, uint64_t *asize, uint64_t *max_asize,
uint64_t *ashift)
{
int numerrors = 0;
int lasterror = 0;
int c;
if (vd->vdev_children == 0) {
vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;
return (SET_ERROR(EINVAL));
}
vdev_open_children(vd);
for (c = 0; c < vd->vdev_children; c++) {
vdev_t *cvd = vd->vdev_child[c];
if (cvd->vdev_open_error) {
lasterror = cvd->vdev_open_error;
numerrors++;
continue;
}
*asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1;
*max_asize = MIN(*max_asize - 1, cvd->vdev_max_asize - 1) + 1;
*ashift = MAX(*ashift, cvd->vdev_ashift);
}
if (numerrors == vd->vdev_children) {
vd->vdev_stat.vs_aux = VDEV_AUX_NO_REPLICAS;
return (lasterror);
}
return (0);
}
static void
vdev_mirror_close(vdev_t *vd)
{
int c;
for (c = 0; c < vd->vdev_children; c++)
vdev_close(vd->vdev_child[c]);
}
static void
vdev_mirror_child_done(zio_t *zio)
{
mirror_child_t *mc = zio->io_private;
mc->mc_error = zio->io_error;
mc->mc_tried = 1;
mc->mc_skipped = 0;
}
static void
vdev_mirror_scrub_done(zio_t *zio)
{
mirror_child_t *mc = zio->io_private;
if (zio->io_error == 0) {
zio_t *pio;
mutex_enter(&zio->io_lock);
while ((pio = zio_walk_parents(zio)) != NULL) {
mutex_enter(&pio->io_lock);
ASSERT3U(zio->io_size, >=, pio->io_size);
bcopy(zio->io_data, pio->io_data, pio->io_size);
mutex_exit(&pio->io_lock);
}
mutex_exit(&zio->io_lock);
}
zio_buf_free(zio->io_data, zio->io_size);
mc->mc_error = zio->io_error;
mc->mc_tried = 1;
mc->mc_skipped = 0;
}
/*
* Check the other, lower-index DVAs to see if they're on the same
* vdev as the child we picked. If they are, use them since they
* are likely to have been allocated from the primary metaslab in
* use at the time, and hence are more likely to have locality with
* single-copy data.
*/
static int
vdev_mirror_dva_select(zio_t *zio, int p)
{
dva_t *dva = zio->io_bp->blk_dva;
mirror_map_t *mm = zio->io_vsd;
int preferred;
int c;
preferred = mm->mm_preferred[p];
for (p--; p >= 0; p--) {
c = mm->mm_preferred[p];
if (DVA_GET_VDEV(&dva[c]) == DVA_GET_VDEV(&dva[preferred]))
preferred = c;
}
return (preferred);
}
static int
vdev_mirror_preferred_child_randomize(zio_t *zio)
{
mirror_map_t *mm = zio->io_vsd;
int p;
if (mm->mm_root) {
p = spa_get_random(mm->mm_preferred_cnt);
return (vdev_mirror_dva_select(zio, p));
}
/*
* To ensure we don't always favour the first matching vdev,
* which could lead to wear leveling issues on SSD's, we
* use the I/O offset as a pseudo random seed into the vdevs
* which have the lowest load.
*/
p = (zio->io_offset >> vdev_mirror_shift) % mm->mm_preferred_cnt;
return (mm->mm_preferred[p]);
}
/*
* Try to find a vdev whose DTL doesn't contain the block we want to read
* prefering vdevs based on determined load.
*
* Try to find a child whose DTL doesn't contain the block we want to read.
* If we can't, try the read on any vdev we haven't already tried.
*/
static int
vdev_mirror_child_select(zio_t *zio)
{
mirror_map_t *mm = zio->io_vsd;
uint64_t txg = zio->io_txg;
int c, lowest_load;
ASSERT(zio->io_bp == NULL || BP_PHYSICAL_BIRTH(zio->io_bp) == txg);
lowest_load = INT_MAX;
mm->mm_preferred_cnt = 0;
for (c = 0; c < mm->mm_children; c++) {
mirror_child_t *mc;
mc = &mm->mm_child[c];
if (mc->mc_tried || mc->mc_skipped)
continue;
if (mc->mc_vd == NULL || !vdev_readable(mc->mc_vd)) {
mc->mc_error = SET_ERROR(ENXIO);
mc->mc_tried = 1; /* don't even try */
mc->mc_skipped = 1;
continue;
}
if (vdev_dtl_contains(mc->mc_vd, DTL_MISSING, txg, 1)) {
mc->mc_error = SET_ERROR(ESTALE);
mc->mc_skipped = 1;
mc->mc_speculative = 1;
continue;
}
mc->mc_load = vdev_mirror_load(mm, mc->mc_vd, mc->mc_offset);
if (mc->mc_load > lowest_load)
continue;
if (mc->mc_load < lowest_load) {
lowest_load = mc->mc_load;
mm->mm_preferred_cnt = 0;
}
mm->mm_preferred[mm->mm_preferred_cnt] = c;
mm->mm_preferred_cnt++;
}
if (mm->mm_preferred_cnt == 1) {
vdev_queue_register_lastoffset(
mm->mm_child[mm->mm_preferred[0]].mc_vd, zio);
return (mm->mm_preferred[0]);
}
if (mm->mm_preferred_cnt > 1) {
int c = vdev_mirror_preferred_child_randomize(zio);
vdev_queue_register_lastoffset(mm->mm_child[c].mc_vd, zio);
return (c);
}
/*
* Every device is either missing or has this txg in its DTL.
* Look for any child we haven't already tried before giving up.
*/
for (c = 0; c < mm->mm_children; c++) {
if (!mm->mm_child[c].mc_tried) {
vdev_queue_register_lastoffset(mm->mm_child[c].mc_vd,
zio);
return (c);
}
}
/*
* Every child failed. There's no place left to look.
*/
return (-1);
}
static void
vdev_mirror_io_start(zio_t *zio)
{
mirror_map_t *mm;
mirror_child_t *mc;
int c, children;
mm = vdev_mirror_map_init(zio);
if (zio->io_type == ZIO_TYPE_READ) {
if ((zio->io_flags & ZIO_FLAG_SCRUB) && !mm->mm_replacing) {
/*
* For scrubbing reads we need to allocate a read
* buffer for each child and issue reads to all
* children. If any child succeeds, it will copy its
* data into zio->io_data in vdev_mirror_scrub_done.
*/
for (c = 0; c < mm->mm_children; c++) {
mc = &mm->mm_child[c];
zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
mc->mc_vd, mc->mc_offset,
zio_buf_alloc(zio->io_size), zio->io_size,
zio->io_type, zio->io_priority, 0,
vdev_mirror_scrub_done, mc));
}
zio_execute(zio);
return;
}
/*
* For normal reads just pick one child.
*/
c = vdev_mirror_child_select(zio);
children = (c >= 0);
} else {
ASSERT(zio->io_type == ZIO_TYPE_WRITE);
/*
* Writes go to all children.
*/
c = 0;
children = mm->mm_children;
}
while (children--) {
mc = &mm->mm_child[c];
zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
zio->io_type, zio->io_priority, 0,
vdev_mirror_child_done, mc));
c++;
}
zio_execute(zio);
}
static int
vdev_mirror_worst_error(mirror_map_t *mm)
{
int c, error[2] = { 0, 0 };
for (c = 0; c < mm->mm_children; c++) {
mirror_child_t *mc = &mm->mm_child[c];
int s = mc->mc_speculative;
error[s] = zio_worst_error(error[s], mc->mc_error);
}
return (error[0] ? error[0] : error[1]);
}
static void
vdev_mirror_io_done(zio_t *zio)
{
mirror_map_t *mm = zio->io_vsd;
mirror_child_t *mc;
int c;
int good_copies = 0;
int unexpected_errors = 0;
for (c = 0; c < mm->mm_children; c++) {
mc = &mm->mm_child[c];
if (mc->mc_error) {
if (!mc->mc_skipped)
unexpected_errors++;
} else if (mc->mc_tried) {
good_copies++;
}
}
if (zio->io_type == ZIO_TYPE_WRITE) {
/*
* XXX -- for now, treat partial writes as success.
*
* Now that we support write reallocation, it would be better
* to treat partial failure as real failure unless there are
* no non-degraded top-level vdevs left, and not update DTLs
* if we intend to reallocate.
*/
/* XXPOLICY */
if (good_copies != mm->mm_children) {
/*
* Always require at least one good copy.
*
* For ditto blocks (io_vd == NULL), require
* all copies to be good.
*
* XXX -- for replacing vdevs, there's no great answer.
* If the old device is really dead, we may not even
* be able to access it -- so we only want to
* require good writes to the new device. But if
* the new device turns out to be flaky, we want
* to be able to detach it -- which requires all
* writes to the old device to have succeeded.
*/
if (good_copies == 0 || zio->io_vd == NULL)
zio->io_error = vdev_mirror_worst_error(mm);
}
return;
}
ASSERT(zio->io_type == ZIO_TYPE_READ);
/*
* If we don't have a good copy yet, keep trying other children.
*/
/* XXPOLICY */
if (good_copies == 0 && (c = vdev_mirror_child_select(zio)) != -1) {
ASSERT(c >= 0 && c < mm->mm_children);
mc = &mm->mm_child[c];
zio_vdev_io_redone(zio);
zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
ZIO_TYPE_READ, zio->io_priority, 0,
vdev_mirror_child_done, mc));
return;
}
/* XXPOLICY */
if (good_copies == 0) {
zio->io_error = vdev_mirror_worst_error(mm);
ASSERT(zio->io_error != 0);
}
if (good_copies && spa_writeable(zio->io_spa) &&
(unexpected_errors ||
(zio->io_flags & ZIO_FLAG_RESILVER) ||
((zio->io_flags & ZIO_FLAG_SCRUB) && mm->mm_replacing))) {
/*
* Use the good data we have in hand to repair damaged children.
*/
for (c = 0; c < mm->mm_children; c++) {
/*
* Don't rewrite known good children.
* Not only is it unnecessary, it could
* actually be harmful: if the system lost
* power while rewriting the only good copy,
* there would be no good copies left!
*/
mc = &mm->mm_child[c];
if (mc->mc_error == 0) {
if (mc->mc_tried)
continue;
if (!(zio->io_flags & ZIO_FLAG_SCRUB) &&
!vdev_dtl_contains(mc->mc_vd, DTL_PARTIAL,
zio->io_txg, 1))
continue;
mc->mc_error = SET_ERROR(ESTALE);
}
zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
mc->mc_vd, mc->mc_offset,
zio->io_data, zio->io_size,
ZIO_TYPE_WRITE, ZIO_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
}
}
}
static void
vdev_mirror_state_change(vdev_t *vd, int faulted, int degraded)
{
if (faulted == vd->vdev_children)
vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
VDEV_AUX_NO_REPLICAS);
else if (degraded + faulted != 0)
vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED, VDEV_AUX_NONE);
else
vdev_set_state(vd, B_FALSE, VDEV_STATE_HEALTHY, VDEV_AUX_NONE);
}
vdev_ops_t vdev_mirror_ops = {
vdev_mirror_open,
vdev_mirror_close,
vdev_default_asize,
vdev_mirror_io_start,
vdev_mirror_io_done,
vdev_mirror_state_change,
NULL,
NULL,
VDEV_TYPE_MIRROR, /* name of this vdev type */
B_FALSE /* not a leaf vdev */
};
vdev_ops_t vdev_replacing_ops = {
vdev_mirror_open,
vdev_mirror_close,
vdev_default_asize,
vdev_mirror_io_start,
vdev_mirror_io_done,
vdev_mirror_state_change,
NULL,
NULL,
VDEV_TYPE_REPLACING, /* name of this vdev type */
B_FALSE /* not a leaf vdev */
};
vdev_ops_t vdev_spare_ops = {
vdev_mirror_open,
vdev_mirror_close,
vdev_default_asize,
vdev_mirror_io_start,
vdev_mirror_io_done,
vdev_mirror_state_change,
NULL,
NULL,
VDEV_TYPE_SPARE, /* name of this vdev type */
B_FALSE /* not a leaf vdev */
};
#if defined(_KERNEL) && defined(HAVE_SPL)
module_param(zfs_vdev_mirror_rotating_inc, int, 0644);
MODULE_PARM_DESC(zfs_vdev_mirror_rotating_inc,
"Rotating media load increment for non-seeking I/O's");
module_param(zfs_vdev_mirror_rotating_seek_inc, int, 0644);
MODULE_PARM_DESC(zfs_vdev_mirror_rotating_seek_inc,
"Rotating media load increment for seeking I/O's");
module_param(zfs_vdev_mirror_rotating_seek_offset, int, 0644);
MODULE_PARM_DESC(zfs_vdev_mirror_rotating_seek_offset,
"Offset in bytes from the last I/O which "
"triggers a reduced rotating media seek increment");
module_param(zfs_vdev_mirror_non_rotating_inc, int, 0644);
MODULE_PARM_DESC(zfs_vdev_mirror_non_rotating_inc,
"Non-rotating media load increment for non-seeking I/O's");
module_param(zfs_vdev_mirror_non_rotating_seek_inc, int, 0644);
MODULE_PARM_DESC(zfs_vdev_mirror_non_rotating_seek_inc,
"Non-rotating media load increment for seeking I/O's");
#endif