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Revert "Reduce latency effects of non-interactive I/O"

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Under certain conditions commit a3a4b8def appears to result in a
hang, or poor performance, when importing a pool.  Until the root
cause can be identified it has been reverted from the release branch.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #11245
This commit is contained in:
Brian Behlendorf
2020-11-30 09:38:15 -08:00
parent a4ab0c607e
commit 2c36eb763f
3 changed files with 18 additions and 145 deletions
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man/man5/zfs-module-parameters.5
+2 -37
View File
@@ -2011,7 +2011,8 @@ Default value: \fB1\fR.
.ad
.RS 12n
The maximum number of I/Os active to each device. Ideally, this will be >=
the sum of each queue's max_active. See the section "ZFS I/O SCHEDULER".
the sum of each queue's max_active. It must be at least the sum of each
queue's min_active. See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1,000\fR.
.RE
@@ -2160,42 +2161,6 @@ See the section "ZFS I/O SCHEDULER".
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_nia_delay\fR (int)
.ad
.RS 12n
For non-interactive I/O (scrub, resilver, removal, initialize and rebuild),
the number of concurrently-active I/O's is limited to *_min_active, unless
the vdev is "idle". When there are no interactive I/Os active (sync or
async), and zfs_vdev_nia_delay I/Os have completed since the last
interactive I/O, then the vdev is considered to be "idle", and the number
of concurrently-active non-interactive I/O's is increased to *_max_active.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_nia_credit\fR (int)
.ad
.RS 12n
Some HDDs tend to prioritize sequential I/O so high, that concurrent
random I/O latency reaches several seconds. On some HDDs it happens
even if sequential I/Os are submitted one at a time, and so setting
*_max_active to 1 does not help. To prevent non-interactive I/Os, like
scrub, from monopolizing the device no more than zfs_vdev_nia_credit
I/Os can be sent while there are outstanding incomplete interactive
I/Os. This enforced wait ensures the HDD services the interactive I/O
within a reasonable amount of time.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na