Re: [PATCH 14/14] block/mq-deadline: Prioritize high-priority requests

[Hannes Reinecke <hare@suse.de>]

On 6/9/21 1:07 AM, Bart Van Assche wrote:
> While one or more requests with a certain I/O priority are pending, do not
> dispatch lower priority requests. Dispatch lower priority requests anyway
> after the "aging" time has expired.
> 
> This patch has been tested as follows:
> 
> modprobe scsi_debug ndelay=1000000 max_queue=16 &&
> sd='' &&
> while [ -z "$sd" ]; do
>   sd=/dev/$(basename /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/*)
> done &&
> echo $((100*1000)) > /sys/block/$sd/queue/iosched/aging_expire &&
> cd /sys/fs/cgroup/blkio/ &&
> echo $$ >cgroup.procs &&
> echo 2 >blkio.prio.class &&
> mkdir -p hipri &&
> cd hipri &&
> echo 1 >blkio.prio.class &&
> { max-iops -a1 -d32 -j1 -e mq-deadline $sd >& ~/low-pri.txt & } &&
> echo $$ >cgroup.procs &&
> max-iops -a1 -d32 -j1 -e mq-deadline $sd >& ~/hi-pri.txt
> 
> Result:
> * 11000 IOPS for the high-priority job
> *   400 IOPS for the low-priority job
> 
> If the aging expiry time is changed from 100s into 0, the IOPS results change
> into 6712 and 6796 IOPS.
> 
> The max-iops script is a script that runs fio with the following arguments:
> --bs=4K --gtod_reduce=1 --ioengine=libaio --ioscheduler=${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@wdc.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  block/mq-deadline-main.c | 42 +++++++++++++++++++++++++++++++++++-----
>  1 file changed, 37 insertions(+), 5 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		        Kernel Storage Architect
hare@suse.de			               +49 911 74053 688
SUSE Software Solutions Germany GmbH, 90409 Nürnberg
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