dm mpath: add service time load balancer
This patch adds a service time oriented dynamic load balancer,
dm-service-time, which selects the path with the shortest estimated
service time for the incoming I/O.
The service time is estimated by dividing the in-flight I/O size
by a performance value of each path.
The performance value can be given as a table argument at the table
loading time. If no performance value is given, all paths are
considered equal.
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 3b311d2..09f93fa 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -258,6 +258,16 @@
If unsure, say N.
+config DM_MULTIPATH_ST
+ tristate "I/O Path Selector based on the service time"
+ depends on DM_MULTIPATH
+ ---help---
+ This path selector is a dynamic load balancer which selects
+ the path expected to complete the incoming I/O in the shortest
+ time.
+
+ If unsure, say N.
+
config DM_DELAY
tristate "I/O delaying target (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL