On 9/28/18 2:42 AM, Ming Lei wrote: > Lot of controllers may have only one irq vector for completing IO > request. And usually affinity of the only irq vector is all possible > CPUs, however, on most of ARCH, there may be only one specific CPU > for handling this interrupt. > > So if all IOs are completed in hardirq context, it is inevitable to > degrade IO performance because of increased irq latency. > > This patch tries to address this issue by allowing to complete request > in softirq context, like the legacy IO path. > > IOPS is observed as ~13%+ in the following randread test on raid0 over > virtio-scsi. > > mdadm --create --verbose /dev/md0 --level=0 --chunk=1024 --raid-devices=8 > /dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg /dev/sdh /dev/sdi > > fio --time_based --name=benchmark --runtime=30 --filename=/dev/md0 > --nrfiles=1 --ioengine=libaio --iodepth=32 --direct=1 --invalidate=1 > --verify=0 --verify_fatal=0 --numjobs=32 --rw=randread --blocksize=4k
Looks fine to me, and imho it makes a lot of sense to apply the same logic for remote completions to single queue as we did for the legacy parts. I have applied it for 4.20. -- Jens Axboe
