On Mon, Sep 27, 2021 at 03:03:28PM -0700, Bart Van Assche wrote:
> In addition to reverting commit 7b05bf771084 ("Revert "block/mq-deadline:
> Prioritize high-priority requests""), this patch uses 'jiffies' instead
> of ktime_get() in the code for aging lower priority requests.
Considering that this is basically a revert of a revert,
except for the ktime_get() to jiffies change, I think that
you should state the reason for this change in the change log.
> Ran the following script:
>
> set -e
> scriptdir=$(dirname "$0")
> if [ -e /sys/module/scsi_debug ]; then modprobe -r scsi_debug; fi
> modprobe scsi_debug ndelay=1000000 max_queue=16
> sd=''
> while [ -z "$sd" ]; do
> sd=$(basename /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/*)
> done
> echo $((100*1000)) > "/sys/block/$sd/queue/iosched/prio_aging_expire"
> if [ -e /sys/fs/cgroup/io.prio.class ]; then
> cd /sys/fs/cgroup
> echo restrict-to-be >io.prio.class
> echo +io > cgroup.subtree_control
> else
> cd /sys/fs/cgroup/blkio/
> echo restrict-to-be >blkio.prio.class
> fi
> echo $$ >cgroup.procs
> mkdir -p hipri
> cd hipri
> if [ -e io.prio.class ]; then
> echo none-to-rt >io.prio.class
> else
> echo none-to-rt >blkio.prio.class
> fi
> { "${scriptdir}/max-iops" -a1 -d32 -j1 -e mq-deadline "/dev/$sd" >& ~/low-pri.txt & }
> echo $$ >cgroup.procs
> "${scriptdir}/max-iops" -a1 -d32 -j1 -e mq-deadline "/dev/$sd" >& ~/hi-pri.txt
>
> Result:
> * 11000 IOPS for the high-priority job
> * 40 IOPS for the low-priority job
>
> If the prio aging expiry time is changed from 100s into 0, the IOPS results
> change into 6712 and 6796 IOPS.
>
> The max-iops script is a script that runs fio with the following arguments:
> --bs=4K --gtod_reduce=1 --ioengine=libaio --ioscheduler=${arg_e} --runtime=60
> --norandommap --rw=read --thread --buffered=0 --numjobs=${arg_j}
> --iodepth=${arg_d} --iodepth_batch_submit=${arg_a}
> --iodepth_batch_complete=$((arg_d / 2)) --name=${positional_argument_1}
> --filename=${positional_argument_1}
>
> Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
> Cc: Niklas Cassel <Niklas.Cassel@xxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
With an elaborated change log, this looks good to me:
Reviewed-by: Niklas Cassel <niklas.cassel@xxxxxxx>
