From: Tim Chase Date: Tue, 25 Apr 2017 04:01:04 +0000 (-0500) Subject: Update documentation for zfs_vdev_queue_depth_pct X-Git-Tag: zfs-0.7.0-rc4~25 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e815485fe9e1716d92e0e0e1e6e4ce1b95d3bb00;p=zfs Update documentation for zfs_vdev_queue_depth_pct It was documented as being related to zfs_vdev_async_max_active when it is actually related to zfs_vdev_async_write_max_active. Also, expand the documentation to describe the allocation throttle which was introduced as part of OpenZFS 7090 in 3dfb57a. Reviewed-by: Richard Yao Reviewed-by: Reviewed-by: George Melikov Reviewed-by: Brian Behlendorf Signed-off-by: Tim Chase Closes #6064 --- diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5 index e34844356..f85c28bf8 100644 --- a/man/man5/zfs-module-parameters.5 +++ b/man/man5/zfs-module-parameters.5 @@ -1151,8 +1151,14 @@ Default value: \fB10\fR. \fBzfs_vdev_queue_depth_pct\fR (int) .ad .RS 12n -The queue depth percentage for each top-level virtual device. -Used in conjunction with zfs_vdev_async_max_active. +Maximum number of queued allocations per top-level vdev expressed as +a percentage of \fBzfs_vdev_async_write_max_active\fR which allows the +system to detect devices that are more capable of handling allocations +and to allocate more blocks to those devices. It allows for dynamic +allocation distribution when devices are imbalanced as fuller devices +will tend to be slower than empty devices. + +See also \fBzio_dva_throttle_enabled\fR. .sp Default value: \fB1000\fR. .RE @@ -1940,6 +1946,8 @@ Default value: \fB30,000\fR. .RS 12n Throttle block allocations in the ZIO pipeline. This allows for dynamic allocation distribution when devices are imbalanced. +When enabled, the maximum number of pending allocations per top-level vdev +is limited by \fBzfs_vdev_queue_depth_pct\fR. .sp Default value: \fB1\fR. .RE