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

[Peter Zijlstra]

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@xxxxxxxxxxxxx> 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.

> >> 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.