Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934702AbdCVTT2 (ORCPT ); Wed, 22 Mar 2017 15:19:28 -0400 Received: from mail-vk0-f41.google.com ([209.85.213.41]:34455 "EHLO mail-vk0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758909AbdCVTTU (ORCPT ); Wed, 22 Mar 2017 15:19:20 -0400 MIME-Version: 1.0 In-Reply-To: <20170322170204.hacokajtuabrjlia@hirez.programming.kicks-ass.net> References: <20170310202341.11449-1-joelaf@google.com> <20170322141626.isj3dlrimppwq2xv@hirez.programming.kicks-ass.net> <20170322170204.hacokajtuabrjlia@hirez.programming.kicks-ass.net> From: Joel Fernandes Date: Wed, 22 Mar 2017 12:19:17 -0700 Message-ID: Subject: Re: [PATCH] sched: fair: Improve PELT decay_load calculation comments To: Peter Zijlstra Cc: LKML , Paul Turner , Dietmar Eggemann , Juri Lelli , Patrick Bellasi , Ingo Molnar Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1552 Lines: 41 Hi Peter, On Wed, Mar 22, 2017 at 10:02 AM, Peter Zijlstra 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 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