I/O Path Selector based on the number of in-flight I/Os

modulename: dm-queue-length.ko

configname: CONFIG_DM_MULTIPATH_QL

Linux Kernel Configuration
└─>Device Drivers
└─>Multiple devices driver support (RAID and LVM)
└─>I/O Path Selector based on the number of in-flight I/Os
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
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.

source code:
drivers/md/dm-queue-length.c