From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965026AbeE2OzN (ORCPT ); Tue, 29 May 2018 10:55:13 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:41914 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964996AbeE2OzK (ORCPT ); Tue, 29 May 2018 10:55:10 -0400 Date: Tue, 29 May 2018 15:55:06 +0100 From: Quentin Perret To: Patrick Bellasi Cc: Vincent Guittot , peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, juri.lelli@redhat.com, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, viresh.kumar@linaro.org, valentin.schneider@arm.com Subject: Re: [PATCH v5 01/10] sched/pelt: Move pelt related code in a dedicated file Message-ID: <20180529145506.GF15173@e108498-lin.cambridge.arm.com> References: <1527253951-22709-1-git-send-email-vincent.guittot@linaro.org> <1527253951-22709-2-git-send-email-vincent.guittot@linaro.org> <20180525142648.GC15173@e108498-lin.cambridge.arm.com> <20180525180455.GF30654@e110439-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180525180455.GF30654@e110439-lin> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 25 May 2018 at 19:04:55 (+0100), Patrick Bellasi wrote: > On 25-May 15:26, Quentin Perret wrote: > > And also, I understand these functions are large, but if we _really_ > > want to inline them even though they're big, why not putting them in > > sched-pelt.h ? > > Had the same tought at first... but then I recalled that header is > generated from a script. Thus, eventually, it should be a different one. Ah, good point. This patch already introduces a pelt.h so I guess that could work as well. > > > We probably wouldn't accept that for everything, but > > those PELT functions are used all over the place, including latency > > sensitive code paths (e.g. task wake-up). > > We should better measure the overheads, if any, and check what > (a modern) compiler does. Maybe some hackbench run could help on the > first point. FWIW, I ran a few hackbench tests today on my Intel box: - Intel i7-6700 (4 cores / 8 threads) @ 3.40GHz - Base kernel: today's tip/sched/core "2539fc82aa9b sched/fair: Update util_est before updating schedutil" - Compiler: GCC 7.3.0 The tables below summarize the results for: perf stat --repeat 10 perf bench sched messaging --pipe --thread -l 50000 --group G Without patch: +---+-------+----------+---------+ | G | Tasks | Duration | Stddev | +---+-------+----------+---------+ | 1 | 40 | 3.906 | +-0.84% | | 2 | 80 | 8.569 | +-0.77% | | 4 | 160 | 16.384 | +-0.46% | | 8 | 320 | 33.686 | +-0.42% | +---+-------+----------+---------+ With patch: +---+-------+----------------+---------+ | G | Tasks | Duration | Stddev | +---+-------+----------------+---------+ | 1 | 40 | 3.953 (+1.2%) | +-1.43% | | 2 | 80 | 8.646 (+0.9%) | +-0.32% | | 4 | 160 | 16.390 (+0.0%) | +-0.38% | | 8 | 320 | 33.992 (+0.9%) | +-0.27% | +---+-------+----------------+---------+ So there is (maybe) a little something on my box, but not so significant IMHO ... :) Thanks, Quentin