On 06/24/18 07:04, Ming Lei wrote:
It isn't necessary to check the host depth in scsi_queue_rq() any more since it has been respected by blk-mq before calling scsi_queue_rq() via getting driver tag. Lots of LUNs may attach to same host, and per-host IOPS may reach millions level, so we should avoid to this expensive atomic operations on the hostwide counter in IO path. This patch implemens scsi_host_busy() via blk_mq_tagset_busy_iter() for reading the count of busy IOs for scsi_mq. It is observed that IOPS is increased by 15% in IO test on scsi_debug (32 LUNs, 32 submit queues, 1024 can_queue, libaio/dio) in one dual-socket system.
Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxx>
