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,URIBL_BLOCKED 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 54D79C43612 for ; Fri, 18 Jan 2019 10:58:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 23A8120823 for ; Fri, 18 Jan 2019 10:58:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547809115; bh=lYGaFjnPnH4xjFjy79/y68qSgQXCTDur8x5h5rhxydw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=zv7TWXAjTDI2fs587yxtskNh+nRSb+a+7sqdXfHquiLk4HdIXe4QKCqgQ7MGiFQ4w Gm0jMe3HDRT1+PaeHLL4Ue6AUrFlgnvvZtZSEQAsBv5vbG2XxlxRKkTkSEYsC9OMlc IA3RAPTT0KwwFp04QXDgSXWSRnX6B2zWik9VcFqc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727505AbfARK6d (ORCPT ); Fri, 18 Jan 2019 05:58:33 -0500 Received: from mail-oi1-f194.google.com ([209.85.167.194]:40830 "EHLO mail-oi1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726809AbfARK6c (ORCPT ); Fri, 18 Jan 2019 05:58:32 -0500 Received: by mail-oi1-f194.google.com with SMTP id t204so8641398oie.7; Fri, 18 Jan 2019 02:58:32 -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=JziQ1Qh8jFaTTCMoH48wl0YfwzuzRkq9NWufSf0sYoo=; b=hUBvV81jlytIxF4WxyZICjBaGwHCByGY/009BILWU5fi36ywgdaQrp2srniyYCZPrN 0ycwdExyVNWlfLtxDKh5uI4dVCt+mDiPcxC++ByJHYEPDGUsT7TsfaOcEQ/aaFZxQhir jPBPjgQxCjQr1nr7en1daxV6yHa95ykCmX0K3/ZOrk/6OG47srsy1s5lg337sZ0aK1ls 3q4hTHgissrnWne7MYx0kDQejjzWxf2RrqNTm2IvYTMqRMIpNrkS7i08VfrPJ5M5uyxV r3Ysg+UsVdX18Hith0bMaCr/3Dl2/M0Xy6gn3Dtrq2XYqYabzGINOzCnaZqhHl2xH0KU pCkg== X-Gm-Message-State: AJcUukdsZywcIeOop0GiqjS0Aw7TFuFOEHCx0AGUG3DY9tyRnGLHjtKK 5JWmnq+cOI0I3mdEHON2MBppAqCNjMCqvrsKTrA= X-Google-Smtp-Source: ALg8bN5XOrCoTr6yZjBjyfj+J8krW9QYY3G0JRHorfNO+0D1yiDArCeS+BfG4NDIfcYr4QP+fw7tiyrQ3Ee5GZWSEo4= X-Received: by 2002:a54:4d01:: with SMTP id v1mr367075oix.246.1547809111788; Fri, 18 Jan 2019 02:58:31 -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> In-Reply-To: <20190118103359.jqctbopx25h3zvqs@queper01-lin> From: "Rafael J. Wysocki" Date: Fri, 18 Jan 2019 11:58:20 +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 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.