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Increase default zfs_rebuild_vdev_limit to 64MB 

When testing distributed rebuild performance with more capable
hardware it was observed than increasing the zfs_rebuild_vdev_limit
to 64M reduced the rebuild time by 17%.  Beyond 64MB there was
some improvement (~2%) but it was not significant when weighed
against the increased memory usage. Memory usage is capped at 1/4
of arc_c_max.

Additionally, vr_bytes_inflight_max has been moved so it's updated
per-metaslab to allow the size to be adjust while a rebuild is
running.

Reviewed-by: Akash B <akash-b@hpe.com>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #14428
This commit is contained in:
Brian Behlendorf 2023-01-24 15:23:32 -08:00
parent c0aea7cf4e
commit 973934b965
2 changed files with 19 additions and 10 deletions
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2
man/man4/zfs.4
View File

@ -1769,7 +1769,7 @@ completes in order to verify the checksums of all blocks which have been
resilvered.
This is enabled by default and strongly recommended.
.
.It Sy zfs_rebuild_vdev_limit Ns = Ns Sy 33554432 Ns B Po 32 MiB Pc Pq u64
.It Sy zfs_rebuild_vdev_limit Ns = Ns Sy 67108864 Ns B Po 64 MiB Pc Pq u64
Maximum amount of I/O that can be concurrently issued for a sequential
resilver per leaf device, given in bytes.
.

27
module/zfs/vdev_rebuild.c
View File

@ -34,6 +34,7 @@
#include <sys/zio.h>
#include <sys/dmu_tx.h>
#include <sys/arc.h>
#include <sys/arc_impl.h>
#include <sys/zap.h>
/*
@ -116,13 +117,12 @@ static uint64_t zfs_rebuild_max_segment = 1024 * 1024;
* segment size is also large (zfs_rebuild_max_segment=1M). This helps keep
* the queue depth short.
*
* 32MB was selected as the default value to achieve good performance with
* a large 90-drive dRAID HDD configuration (draid2:8d:90c:2s). A sequential
* rebuild was unable to saturate all of the drives using smaller values.
* With a value of 32MB the sequential resilver write rate was measured at
* 800MB/s sustained while rebuilding to a distributed spare.
* 64MB was observed to deliver the best performance and set as the default.
* Testing was performed with a 106-drive dRAID HDD pool (draid2:11d:106c)
* and a rebuild rate of 1.2GB/s was measured to the distribute spare.
* Smaller values were unable to fully saturate the available pool I/O.
*/
static uint64_t zfs_rebuild_vdev_limit = 32 << 20;
static uint64_t zfs_rebuild_vdev_limit = 64 << 20;
/*
* Automatically start a pool scrub when the last active sequential resilver
@ -754,6 +754,7 @@ vdev_rebuild_thread(void *arg)
{
vdev_t *vd = arg;
spa_t *spa = vd->vdev_spa;
vdev_t *rvd = spa->spa_root_vdev;
int error = 0;
/*
@ -786,9 +787,6 @@ vdev_rebuild_thread(void *arg)
vr->vr_pass_bytes_scanned = 0;
vr->vr_pass_bytes_issued = 0;
vr->vr_bytes_inflight_max = MAX(1ULL << 20,
zfs_rebuild_vdev_limit * vd->vdev_children);
uint64_t update_est_time = gethrtime();
vdev_rebuild_update_bytes_est(vd, 0);
@ -804,6 +802,17 @@ vdev_rebuild_thread(void *arg)
metaslab_t *msp = vd->vdev_ms[i];
vr->vr_scan_msp = msp;
/*
* Calculate the max number of in-flight bytes for top-level
* vdev scanning operations (minimum 1MB, maximum 1/4 of
* arc_c_max shared by all top-level vdevs). Limits for the
* issuing phase are done per top-level vdev and are handled
* separately.
*/
uint64_t limit = (arc_c_max / 4) / MAX(rvd->vdev_children, 1);
vr->vr_bytes_inflight_max = MIN(limit, MAX(1ULL << 20,
zfs_rebuild_vdev_limit * vd->vdev_children));
/*
* Removal of vdevs from the vdev tree may eliminate the need
* for the rebuild, in which case it should be canceled. The