linux-kernel - Re: [PATCHSET block/for-next] IO cost model based work-conserving porportional controller

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Message-ID: <20190902155652.GH2263813@devbig004.ftw2.facebook.com>
Date:   Mon, 2 Sep 2019 08:56:52 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Paolo Valente <paolo.valente@...aro.org>
Cc:     Jens Axboe <axboe@...nel.dk>, newella@...com, clm@...com,
        Josef Bacik <josef@...icpanda.com>, dennisz@...com,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>, kernel-team@...com,
        cgroups@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        kafai@...com, songliubraving@...com, yhs@...com,
        bpf@...r.kernel.org
Subject: Re: [PATCHSET block/for-next] IO cost model based work-conserving
 porportional controller

On Mon, Sep 02, 2019 at 05:45:50PM +0200, Paolo Valente wrote:
> Thanks for this extra explanations.  It is a little bit difficult for
> me to understand how the min/max teaks for exactly, but you did give
> me the general idea.

It just limits how far high and low the IO issue rate, measured in
cost, can go.  ie. if max is at 200%, the controller won't issue more
than twice of what the cost model says 100% is.

> Are these results in line with your expectations?  If they are, then
> I'd like to extend benchmarks to more mixes of workloads.  Or should I
> try some other QoS configuration first?

They aren't.  Can you please include the content of io.cost.qos and
io.cost.model before each run?  Note that partial writes to subset of
parameters don't clear other parameters.

Thanks.

-- 
tejun