linux-kernel - RE: Device or HBA level QD throttling creates randomness in sequetial workload

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Message-ID: <1f7cec69e6e12b6baa8e7f180a8e41b3@mail.gmail.com>
Date:   Mon, 24 Oct 2016 18:35:01 +0530
From:   Kashyap Desai <kashyap.desai@...adcom.com>
To:     Omar Sandoval <osandov@...ndov.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, axboe@...nel.dk,
        Christoph Hellwig <hch@...radead.org>, paolo.valente@...aro.org
Subject: RE: Device or HBA level QD throttling creates randomness in sequetial workload

>
> On Fri, Oct 21, 2016 at 05:43:35PM +0530, Kashyap Desai wrote:
> > Hi -
> >
> > I found below conversation and it is on the same line as I wanted some
> > input from mailing list.
> >
> > http://marc.info/?l=linux-kernel&m=147569860526197&w=2
> >
> > I can do testing on any WIP item as Omar mentioned in above
discussion.
> > https://github.com/osandov/linux/tree/blk-mq-iosched

I tried build kernel using this repo, but looks like it is not allowed to
reboot due to some changes in <block> layer.

>
> Are you using blk-mq for this disk? If not, then the work there won't
affect you.

YES. I am using blk-mq for my test. I also confirm if use_blk_mq is
disable, Sequential work load issue is not seen and <cfq> scheduling works
well.

>
> > Is there any workaround/alternative in latest upstream kernel, if user
> > wants to see limited penalty  for Sequential Work load on HDD ?
> >
> > ` Kashyap
> >