From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AC58C28CF6 for ; Wed, 1 Aug 2018 09:23:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 425A320844 for ; Wed, 1 Aug 2018 09:23:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 425A320844 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388822AbeHALIa (ORCPT ); Wed, 1 Aug 2018 07:08:30 -0400 Received: from foss.arm.com ([217.140.101.70]:38168 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732437AbeHALIa (ORCPT ); Wed, 1 Aug 2018 07:08:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 93F5918A; Wed, 1 Aug 2018 02:23:40 -0700 (PDT) Received: from queper01-ThinkPad-T460s (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DD27C3F5BA; Wed, 1 Aug 2018 02:23:33 -0700 (PDT) Date: Wed, 1 Aug 2018 10:23:27 +0100 From: Quentin Perret To: "Rafael J. Wysocki" Cc: Saravana Kannan , Peter Zijlstra , "Rafael J. Wysocki" , Linux Kernel Mailing List , Linux PM , Greg Kroah-Hartman , Ingo Molnar , Dietmar Eggemann , Morten Rasmussen , Chris Redpath , Patrick Bellasi , Valentin Schneider , Vincent Guittot , Thara Gopinath , Viresh Kumar , Todd Kjos , Joel Fernandes , Steve Muckle , adharmap@quicinc.com, skannan@quicinc.com, Pavan Kondeti , Juri Lelli , Eduardo Valentin , Srinivas Pandruvada , currojerez@riseup.net, Javi Merino , linux-pm-owner@vger.kernel.org Subject: Re: [PATCH v5 10/14] sched/cpufreq: Refactor the utilization aggregation method Message-ID: <20180801092325.g2upcivcvdo62hub@queper01-ThinkPad-T460s> References: <20180724122521.22109-1-quentin.perret@arm.com> <20180724122521.22109-11-quentin.perret@arm.com> <331552975e858911db66bc78c2c8e720@codeaurora.org> <20180731075950.tfvxef6yuja3ad2k@queper01-lin> <75f415911ccdd02d6fd217ca1c7d8902@codeaurora.org> <20180801082353.egym4tsbr7ppql27@queper01-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 01 Aug 2018 at 10:35:32 (+0200), Rafael J. Wysocki wrote: > On Wed, Aug 1, 2018 at 10:23 AM, Quentin Perret wrote: > > On Wednesday 01 Aug 2018 at 09:32:49 (+0200), Rafael J. Wysocki wrote: > >> On Tue, Jul 31, 2018 at 9:31 PM, wrote: > >> >> On Monday 30 Jul 2018 at 12:35:27 (-0700), skannan@codeaurora.org wrote: > >> >>> If it's going to be a different aggregation from what's done for > >> >>> frequency > >> >>> guidance, I don't see the point of having this inside schedutil. Why not > >> >>> keep it inside the scheduler files? > >> >> > >> >> This code basically results from a discussion we had with Peter on v4. > >> >> Keeping everything centralized can make sense from a maintenance > >> >> perspective, I think. That makes it easy to see the impact of any change > >> >> to utilization signals for both EAS and schedutil. > >> > > >> > In that case, I'd argue it makes more sense to keep the code centralized in > >> > the scheduler. The scheduler can let schedutil know about the utilization > >> > after it aggregates them. There's no need for a cpufreq governor to know > >> > that there are scheduling classes or how many there are. And the scheduler > >> > can then choose to aggregate one way for task packing and another way for > >> > frequency guidance. > >> > >> Also the aggregate utilization may be used by cpuidle governors in > >> principle to decide how deep they can go with idle state selection. > > > > The only issue I see with this right now is that some of the things done > > in this function are policy decisions which really belong to the governor, > > I think. > > Well, the scheduler makes policy decisions too, in quite a few places. :-) That is true ... ;-) But not so much about frequency selection yet I guess > The really important consideration here is whether or not there may be > multiple governors making different policy decisions in that respect. > If not, then where exactly the single policy decision is made doesn't > particularly matter IMO. I think some users of the aggregated utilization signal do want to make slightly different decisions (I'm thinking about the RT-go-to-max thing again which makes perfect sense in sugov, but could possibly hurt EAS). So the "hard" part of this work is to figure out what really is a governor-specific policy decision, and what is common between all users. I put "hard" between quotes because I only see the case of RT as truly sugov-specific for now. If we also want a special case for DL, Peter's enum should work OK, and enable to add more special cases for new users (cpuidle ?) if needed. But maybe that is something for later ? Thanks, Quentin