linux-kernel - Re: [PATCH 1/2] sched/deadline: accurate reclaim bandwidth for GRUB

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Message-ID: <CAO7JXPg9K4MA7H63Num8-BHBT-Y=GQ3BnEEvaEMVKmYsXCY7Sg@mail.gmail.com>
Date:   Thu, 11 May 2023 16:40:46 -0400
From:   Vineeth Remanan Pillai <vineeth@...byteword.org>
To:     luca abeni <luca.abeni@...tannapisa.it>
Cc:     Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Valentin Schneider <vschneid@...hat.com>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/2] sched/deadline: accurate reclaim bandwidth for GRUB

> >
> > I felt that, since we are using sequential reclaim mentioned in the
> > paper and we isolate all parameters per-cpu(except for extra_bw) we
> > could use the "-dq = -(U/Umax) dt" equation as it was simpler than
> > equation (3).
>
> This is the part I am not sure about...
>
> Maybe the best way to go is to split the patch: first you implement (1)
> (and use div64 to remove the approximation I used), then you implement
> (3) in a second patch.
>
> Finally, if removing the max{} is really needed you can do it in a
> third patch (but I would try to go with Equation 3 before removing the
> max{})
>
Sure, I shall split the patch. Joel also suggested splitting the patch
and I was probably wrong to think that the patch was simple to be a
single patch :-).

Since equation (3) has theoretical backing, I am perfectly fine with
using it for our fix. Will have 2 patches as you suggested.

Will get the v3 out soon..

Thanks,
Vineeth