Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments

From	Joel Fernandes <joelaf@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments
Date	2017-03-22 20:20 +0100
Message-ID	<tnTXz-7mv-11@gated-at.bofh.it> (permalink)
References	<tjzkK-Cj-13@gated-at.bofh.it> <tnPhf-3Fu-15@gated-at.bofh.it> <tnRsK-5on-25@gated-at.bofh.it> <tnRVL-5RD-7@gated-at.bofh.it>
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Hi Peter,

On Wed, Mar 22, 2017 at 10:02 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Mar 22, 2017 at 09:35:43AM -0700, Joel Fernandes wrote:
>> On Wed, Mar 22, 2017 at 7:16 AM, Peter Zijlstra <peterz@infradead.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.
>
> Must be me then, because I've never been confused about that. Esp. so
> since the first part: y^p = 1/2, explicitly mentions half. So its clear
> from the factorization that half is meant.

Yes that's true.

>> >> 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?
>
> I think the fact that there's now words actually makes it worse.
>
> The equation very concisely shows what we do. I don't see why we need
> extra words there to obscure things.

Ok, I agree with you and will kill this patch then. Thanks for the review.

Regards,
Joel

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Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments Peter Zijlstra <peterz@infradead.org> - 2017-03-22 15:20 +0100
  Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments Joel Fernandes <joelaf@google.com> - 2017-03-22 17:40 +0100
    Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments Peter Zijlstra <peterz@infradead.org> - 2017-03-22 18:10 +0100
      Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments Joel Fernandes <joelaf@google.com> - 2017-03-22 20:20 +0100

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