Re: [PATCH 0/5] blk-mq/scsi-mq: support global tags & introduce force_blk_mq

Ming Lei
2018-02-07T12:23:02Z

On Wed, Feb 07, 2018 at 07:50:21AM +0100, Hannes Reinecke wrote:
> Hi all,
>
> [ .. ]
> >>
> >> Could you share us your patch for enabling global_tags/MQ on
> > megaraid_sas
> >> so that I can reproduce your test?
> >>
> >>> See below perf top data. "bt_iter" is consuming 4 times more CPU.
> >>
> >> Could you share us what the IOPS/CPU utilization effect is after
> > applying the
> >> patch V2? And your test script?
> > Regarding CPU utilization, I need to test one more time. Currently system
> > is in used.
> >
> > I run below fio test on total 24 SSDs expander attached.
> >
> > numactl -N 1 fio jbod.fio --rw=randread --iodepth=64 --bs=4k
> > --ioengine=libaio --rw=randread
> >
> > Performance dropped from 1.6 M IOPs to 770K IOPs.
> >
> This is basically what we've seen with earlier iterations.

Hi Hannes,

As I mentioned in another mail[1], Kashyap's patch has a big issue, which
causes only reply queue 0 used.

[1] https://marc.info/?l=linux-scsi&m=151793204014631&w=2

So could you guys run your performance test again after fixing the patch?

Thanks,
Ming