On Mon, Mar 07, 2022 at 06:39:54PM -0600, Mike Christie wrote: > The software iscsi driver's queuecommand can block and taking the extra > hop from kblockd to its workqueue results in a performance hit. Allowing > it to set BLK_MQ_F_BLOCKING and transmit from that context directly > results in a 20-30% improvement in IOPs for workloads like: > > fio --filename=/dev/sdb --direct=1 --rw=randrw --bs=4k --ioengine=libaio > --iodepth=128 --numjobs=1 > > and for all write workloads. This single patch shouldn't make any difference for iscsi, so please make it as last one if performance improvement data is provided in commit log. Also is there performance effect for other worloads? such as multiple jobs? iscsi is SQ hardware, so if driver is blocked in ->queuecommand() via BLK_MQ_F_BLOCKING, other contexts can't submit IO to scsi ML any more. thanks, Ming
