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From:   Ming Lei <tom.leiming@gmail.com>
Date:   Thu, 23 Jan 2020 09:40:38 +0800
Message-ID: <CACVXFVN2QteGv=mWpVimZ9y2yzLZOOthB9muFsxTG3LkWWpwfA@mail.gmail.com>
Subject: Re: Re [PATCH] Adding multiple workers to the loop device.
To:     "muraliraja.muniraju" <muraliraja.muniraju@rubrik.com>
Cc:     Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
        Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Jan 22, 2020 at 4:11 AM muraliraja.muniraju
<muraliraja.muniraju@rubrik.com> wrote:
>
> Below is the dd results that I ran with the worker and without the worker changes.
> Enhanced Loop has the changes and ran with 1,2,3,4 workers with 4 dds running on the same loop device.
> Normal Loop is 1 worker(the existing code) with 4 dd's running on the same loop device.
> Enhanced loop
> 1 - READ: io=21981MB, aggrb=187558KB/s, minb=187558KB/s, maxb=187558KB/s, mint=120008msec, maxt=120008msec
> 2 - READ: io=41109MB, aggrb=350785KB/s, minb=350785KB/s, maxb=350785KB/s, mint=120004msec, maxt=120004msec
> 3 - READ: io=45927MB, aggrb=391802KB/s, minb=391802KB/s, maxb=391802KB/s, mint=120033msec, maxt=120033msec
> 4 - READ: io=45771MB, aggrb=390543KB/s, minb=390543KB/s, maxb=390543KB/s, mint=120011msec, maxt=120011msec
> Normal loop
> 1 - READ: io=18432MB, aggrb=157201KB/s, minb=157201KB/s, maxb=157201KB/s, mint=120065msec, maxt=120065msec
> 2 - READ: io=18762MB, aggrb=160035KB/s, minb=160035KB/s, maxb=160035KB/s, mint=120050msec, maxt=120050msec
> 3 - READ: io=18174MB, aggrb=155058KB/s, minb=155058KB/s, maxb=155058KB/s, mint=120020msec, maxt=120020msec
> 4 - READ: io=20559MB, aggrb=175407KB/s, minb=175407KB/s, maxb=175407KB/s, mint=120020msec, maxt=120020msec

Could you share your exact test command?

Multiple jobs may hurt performance in case of sequential IOs on HDD backend.
Also the 1st version of the loop dio patch uses normal wq, I remembered that
random IOperformance isn't improved much, meantime sequential IO perf drops
with normal wq, whentesting SSD backend.

So I took kthread worker.

Thanks,
Ming Lei