Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753862AbbLOMrQ (ORCPT ); Tue, 15 Dec 2015 07:47:16 -0500 Received: from mail-lf0-f54.google.com ([209.85.215.54]:32972 "EHLO mail-lf0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751797AbbLOMrO (ORCPT ); Tue, 15 Dec 2015 07:47:14 -0500 MIME-Version: 1.0 In-Reply-To: <20151215122015.GA6357@twins.programming.kicks-ass.net> References: <1449641971-20827-1-git-send-email-smuckle@linaro.org> <1449641971-20827-10-git-send-email-smuckle@linaro.org> <20151214151729.GQ6357@twins.programming.kicks-ass.net> <20151214221231.39b5bc4e@luca-1225C> <566FD446.1080004@unitn.it> <20151215122015.GA6357@twins.programming.kicks-ass.net> From: Vincent Guittot Date: Tue, 15 Dec 2015 13:46:53 +0100 Message-ID: Subject: Re: [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in scale_rt_capacity To: Peter Zijlstra Cc: Luca Abeni , Steve Muckle , Ingo Molnar , linux-kernel , "linux-pm@vger.kernel.org" , Morten Rasmussen , Dietmar Eggemann , Juri Lelli , Patrick Bellasi , Michael Turquette 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: 1762 Lines: 37 On 15 December 2015 at 13:20, Peter Zijlstra wrote: > On Tue, Dec 15, 2015 at 09:50:14AM +0100, Luca Abeni wrote: >> On 12/15/2015 05:59 AM, Vincent Guittot wrote: > >> >The 2nd definition is used to compute the remaining capacity for the >> >CFS scheduler. This one doesn't need to be updated at each wake/sleep >> >of a deadline task but should reflect the capacity used by deadline in >> >a larger time scale. The latter will be used by the CFS scheduler at >> >the periodic load balance pace > >> Ok, so as I wrote above this really looks like an average utilisation. >> My impression (but I do not know the CFS code too much) is that the mainline >> kernel is currently doing the right thing to compute it, so maybe there is no >> need to change the current code in this regard. >> If the current code is not acceptable for some reason, an alternative would >> be to measure the active utilisation for frequency scaling, and then apply a >> low-pass filter to it for CFS. > > So CFS really only needs a 'vague' average idea on how much time it will > not get. Its best effort etc., so being a little wrong isn't a problem. > > The current code suffices, but I think the reason its been changed in > this series is that they want/need separate tracking for fifo/rr and > deadline in the next patch, and taking out deadline like proposed was > the easiest way of achieving that. yes. you're right. The goal was to minimize the overhead for tracking separately fifo/rr and deadline. > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/