dm mpath: add queue length load balancer
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>
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 36e0675..3b311d2 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -249,6 +249,15 @@
---help---
Allow volume managers to support multipath hardware.
+config DM_MULTIPATH_QL
+ tristate "I/O Path Selector based on the number of in-flight I/Os"
+ depends on DM_MULTIPATH
+ ---help---
+ This path selector is a dynamic load balancer which selects
+ the path with the least number of in-flight I/Os.
+
+ If unsure, say N.
+
config DM_DELAY
tristate "I/O delaying target (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL