linux-kernel - Re: [PATCH] sched: fair: Improve PELT decay

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Message-ID: <CAJWu+ooHy9GQEsYuaTS1Pw6yjL=MMex7056P+pzqNP5OaOgrwg@mail.gmail.com>
Date:   Wed, 22 Mar 2017 09:35:43 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Paul Turner <pjt@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Juri Lelli <Juri.Lelli@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments

On Wed, Mar 22, 2017 at 7:16 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Fri, Mar 10, 2017 at 12:23:41PM -0800, Joel Fernandes wrote:
>> The PELT decay_load comments are a bit confusing, first of all
>> the 1/2^N should be (1/2)^N so that the reader doesn't get confused.
>
> I'm thinking you're confused. They're identical.
>
> (1/2)^N = (2^-1)^N = 2^-N = 1/2^N

They are identical I know, but I meant by enclosing the 1/2 in
brackets, it is more clear that we multiply by 1/2 N times to the
first time reader - for the reason that we'd like to reduce the PELT
calculated load by 1/2 N times.

>> Secondly, the y^N splitting into a 2-part decay factor deserves
>> a better explanation. This patch improves the comments.
>
> I find its actually harder to read.

Oh, which part? Can you help improve it? Maybe I didn't word something
correctly?

Regards,
Joel