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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS 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 469B7C43444 for ; Fri, 18 Jan 2019 11:21:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB47F2086D for ; Fri, 18 Jan 2019 11:21:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547810476; bh=3xR3UHPPsBhd0jT3nT2Bv7YIWUSdVbnoyYAEqpVbYWc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=1l7onzePBVQqqrM1VPV2+mSZEHICw9Q4II7wbYsEP+VvxaSxautXMGdEhN1iGBPs8 6rVFo98HWntTOjlCBmIENUaUGGfwpoowQoTXH+FzcuHHZVEWP3TEYEcbwXRyIL5htk nSSX3sQolB5VWke/EBKK43CadQP3kLUrtNC1c0Kc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727277AbfARLVN (ORCPT ); Fri, 18 Jan 2019 06:21:13 -0500 Received: from mail-ot1-f68.google.com ([209.85.210.68]:42756 "EHLO mail-ot1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727037AbfARLVN (ORCPT ); Fri, 18 Jan 2019 06:21:13 -0500 Received: by mail-ot1-f68.google.com with SMTP id v23so14034008otk.9; Fri, 18 Jan 2019 03:21:09 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=0+QBcQrorh2AK/jwGzYU0QQmBWvHjU2sSTpXbqlhOQA=; b=GqfB50/Zsou+v/nfpPGfiy+io8MvX1pPRAt8wOVrUHpqE40p1VZW+C2UZTaahBALa5 9HVshlWxwMovnU7E9kO0ZyVeTiRTHwwqr2ui13hdHNMcSIvVbNL876dy6e6dUr7Su2yw h3FUd68EpD+YZlqTzxSLFpUM/jdiDsfwjWfij5XimWQmje8tARoG0tprUEJiOs0VhdZl /araWHFBHqHePX60bBONdYpixY8k37froh3aNjE+aP3KeLfEEv+F25HkM3wGiJnIPdSv /Z2qqYU+6RZHfPS9f3ffZYrNf8kuPc+YdXvE6hcqa7xPh6aXbb1NLajp0OqLA3HA0Sso 5t9g== X-Gm-Message-State: AJcUukfm7TBk5fI5CiCWMDdv/5+V9UHMllhUgHPvsBXeJLlTakeW1qEn D6zLvK5ieyB0ScoDJKSWKrUyHI8sLWgQr4oUfrc= X-Google-Smtp-Source: ALg8bN6cqjnat/FlraN3PUnBxgYauHozo445xE1iRQKe823kOWi5XgeU1KRx0FQtx8BmW1DBSC5t1V+z73/u6rWbu+s= X-Received: by 2002:a9d:2062:: with SMTP id n89mr10730511ota.244.1547810468436; Fri, 18 Jan 2019 03:21:08 -0800 (PST) MIME-Version: 1.0 References: <20190110110546.8101-1-quentin.perret@arm.com> <20190110110546.8101-3-quentin.perret@arm.com> <20190117155117.GG14385@localhost.localdomain> <20190118091652.xn6iw52tccwh6vap@queper01-lin> <20190118103359.jqctbopx25h3zvqs@queper01-lin> <20190118111114.dytdk7oq63illgkg@queper01-lin> In-Reply-To: <20190118111114.dytdk7oq63illgkg@queper01-lin> From: "Rafael J. Wysocki" Date: Fri, 18 Jan 2019 12:20:57 +0100 Message-ID: Subject: Re: [PATCH 2/2] sched: Document Energy Aware Scheduling To: Quentin Perret Cc: "Rafael J. Wysocki" , Juri Lelli , Jonathan Corbet , Peter Zijlstra , "Rafael J. Wysocki" , Ingo Molnar , Morten Rasmussen , qais.yousef@arm.com, Patrick Bellasi , Dietmar Eggemann , "open list:DOCUMENTATION" , Linux PM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 18, 2019 at 12:11 PM Quentin Perret wrote: > > On Friday 18 Jan 2019 at 12:01:35 (+0100), Rafael J. Wysocki wrote: > > On Fri, Jan 18, 2019 at 11:58 AM Rafael J. Wysocki wrote: > > > > > > On Fri, Jan 18, 2019 at 11:34 AM Quentin Perret wrote: > > > > > > > > Hi Rafael, > > > > > > > > On Friday 18 Jan 2019 at 10:57:08 (+0100), Rafael J. Wysocki wrote: > > > > > On Fri, Jan 18, 2019 at 10:16 AM Quentin Perret wrote: > > > > > > > > > > > > Hi Juri, > > > > > > > > > > > > On Thursday 17 Jan 2019 at 16:51:17 (+0100), Juri Lelli wrote: > > > > > > > On 10/01/19 11:05, Quentin Perret wrote: > > > > > > [...] > > > > > > > > +The idea behind introducing an EM is to allow the scheduler to evaluate the > > > > > > > > +implications of its decisions rather than blindly applying energy-saving > > > > > > > > +techniques that may have positive effects only on some platforms. At the same > > > > > > > > +time, the EM must be as simple as possible to minimize the scheduler latency > > > > > > > > +impact. > > > > > > > > + > > > > > > > > +In short, EAS changes the way CFS tasks are assigned to CPUs. When it is time > > > > > > > > > > > > > > Not sure if we want to remark the fact that EAS is looking at CFS tasks > > > > > > > only ATM. > > > > > > > > > > > > Oh, what's wrong about mentioning it ? I mean, it is a fact ATM ... > > > > > > > > > > But it won't hurt to mention that it may cover other scheduling > > > > > classes in the future. IOW, the scope limit is not fundamental. > > > > > > > > Agreed, I can do that. > > > > > > > > > > > > +for the scheduler to decide where a task should run (during wake-up), the EM > > > > > > > > +is used to break the tie between several good CPU candidates and pick the one > > > > > > > > +that is predicted to yield the best energy consumption without harming the > > > > > > > > +system's throughput. The predictions made by EAS rely on specific elements of > > > > > > > > +knowledge about the platform's topology, which include the 'capacity' of CPUs, > > > > > > > > > > > > > > Add a reference to DT bindings docs defining 'capacity' (or define it > > > > > > > somewhere)? > > > > > > > > > > > > Right, I can mention this is defined in the next section. But are you > > > > > > sure about the reference to the DT bindings ? They're arm-specific right ? > > > > > > Maybe I can give that as an example or something ... > > > > > > > > > > Example sounds right. > > > > > > > > > > You also can point to the section below from here. > > > > > > > > Sounds good. > > > > > > > > > Side note: If the doc is in the .rst format (which Peter won't like > > > > > I'm sure :-)), you can actually use cross-references in it and you get > > > > > a translation to an HTML doc (hosted at kernel.org) for free and the > > > > > cross-references become clickable links in that. > > > > > > > > Right, I personally don't mind the .rst format, but the existing files > > > > in Documentation/power/ and Documentation/scheduler/ are good old txt > > > > files so I just wanted to keep things consistent. > > > > > > In fact, Documentation/power/ is under a slow on-going transition to > > > .rst (due to the benefits mentioned above). > > > > > > > I don't mind converting to rst if necessary :-) > > > > > > It is not necessary, but maybe worth considering. > > > > That said, as this is targeted at Documentation/scheduler/, being > > consistent with the other material in there is probably more > > important. > > Right. Patch 01/02 is targeted at Documentation/power/ though. So if > that makes your life easier I can turn that one into a .rst file, no > problem at all. Yes, I'd prefer it that way. And please put it into Documentation/driver-api/pm/.