linux-kernel - Re: bfq-mq performance comparison to cfq

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Message-ID: <1491837330.4199.1.camel@sandisk.com>
Date:   Mon, 10 Apr 2017 15:15:31 +0000
From:   Bart Van Assche <Bart.VanAssche@...disk.com>
To:     "aherrmann@...e.com" <aherrmann@...e.com>,
        "paolo.valente@...aro.org" <paolo.valente@...aro.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>
Subject: Re: bfq-mq performance comparison to cfq

On Mon, 2017-04-10 at 11:55 +0200, Paolo Valente wrote:
> That said, if you do always want maximum throughput, even at the
> expense of latency, then just switch off low-latency heuristics, i.e.,
> set low_latency to 0.  Depending on the device, setting slice_ilde to
> 0 may help a lot too (as well as with CFQ).  If the throughput is
> still low also after forcing BFQ to an only-throughput mode, then you
> hit some bug, and I'll have a little more work to do ...

Hello Paolo,

Has it been considered to make applications tell the I/O scheduler
whether to optimize for latency or for throughput? It shouldn't be that
hard for window managers and shells to figure out whether or not a new
application that is being started is interactive or not. This would
require a mechanism that allows applications to provide such information
to the I/O scheduler. Wouldn't that be a better approach than the I/O
scheduler trying to guess whether or not an application is an interactive
application?

Bart.