blk-mq with SAS SSD

blk-mq in RHEL 7.2

It can improve performance by allowing certain device drivers to map I/O requests to multiple hardware or software queues.
If the dm_mod.use_blk_mq=y kernel option is specified. The default value is n (disabled).
It may be beneficial to set dm_mod.use_blk_mq=y if the underlying SCSI devices are also using blk-mq, as doing so reduces locking overhead at the DM layer.
To determine whether DM multipath is using blk-mq on a system, cat the file /sys/block/dm-X/dm/use_blk_mq, where dm-X is replaced by the DM multipath device of interest. This file is read-only and reflects what the global value in /sys/module/dm_mod/parameters/use_blk_mq was at the time the request-based DM multipath device was created.

High Performance Storage with blk-mq and scsi-mq
Increasing SCSI LLD Driver Performance by Using the SCSI Multiqueue Approach
Linux Multi-Queue Block IO Queueing Mechanism)
blk-mq SCSI performance