mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-23 04:34:11 +08:00
fd5e033908
This patch adds a dynamic load balancer, dm-queue-length, which balances the number of in-flight I/Os across the paths. The code is based on the patch posted by Stefan Bader: https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html Signed-off-by: Stefan Bader <stefan.bader@canonical.com> Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
40 lines
1.2 KiB
Plaintext
40 lines
1.2 KiB
Plaintext
dm-queue-length
|
|
===============
|
|
|
|
dm-queue-length is a path selector module for device-mapper targets,
|
|
which selects a path with the least number of in-flight I/Os.
|
|
The path selector name is 'queue-length'.
|
|
|
|
Table parameters for each path: [<repeat_count>]
|
|
<repeat_count>: The number of I/Os to dispatch using the selected
|
|
path before switching to the next path.
|
|
If not given, internal default is used. To check
|
|
the default value, see the activated table.
|
|
|
|
Status for each path: <status> <fail-count> <in-flight>
|
|
<status>: 'A' if the path is active, 'F' if the path is failed.
|
|
<fail-count>: The number of path failures.
|
|
<in-flight>: The number of in-flight I/Os on the path.
|
|
|
|
|
|
Algorithm
|
|
=========
|
|
|
|
dm-queue-length increments/decrements 'in-flight' when an I/O is
|
|
dispatched/completed respectively.
|
|
dm-queue-length selects a path with the minimum 'in-flight'.
|
|
|
|
|
|
Examples
|
|
========
|
|
In case that 2 paths (sda and sdb) are used with repeat_count == 128.
|
|
|
|
# echo "0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128" \
|
|
dmsetup create test
|
|
#
|
|
# dmsetup table
|
|
test: 0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128
|
|
#
|
|
# dmsetup status
|
|
test: 0 10 multipath 2 0 0 0 1 1 E 0 2 1 8:0 A 0 0 8:16 A 0 0
|