Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757998AbcCCPi2 (ORCPT ); Thu, 3 Mar 2016 10:38:28 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:36366 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756770AbcCCPi0 (ORCPT ); Thu, 3 Mar 2016 10:38:26 -0500 Date: Thu, 3 Mar 2016 16:38:17 +0100 From: Peter Zijlstra To: Vincent Guittot Cc: "Rafael J. Wysocki" , "Rafael J. Wysocki" , Linux PM list , Juri Lelli , Steve Muckle , ACPI Devel Maling List , Linux Kernel Mailing List , Srinivas Pandruvada , Viresh Kumar , Michael Turquette Subject: Re: [PATCH 6/6] cpufreq: schedutil: New governor based on scheduler utilization data Message-ID: <20160303153817.GO6344@twins.programming.kicks-ass.net> References: <2495375.dFbdlAZmA6@vostro.rjw.lan> <1842158.0Xhak3Uaac@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 714 Lines: 14 On Thu, Mar 03, 2016 at 03:01:15PM +0100, Vincent Guittot wrote: > > In case a more formal derivation of this formula is needed, it is > > based on the following 3 assumptions: > > > > (1) Performance is a linear function of frequency. > > (2) Required performance is a linear function of the utilization ratio > > x = util/max as provided by the scheduler (0 <= x <= 1). > > Just to mention that the utilization that you are using, varies with > the frequency which add another variable in your equation Right, x86 hasn't implemented arch_scale_freq_capacity(), so the utilization values we use are all over the map. If we lower freq, the util will go up, which would result in us bumping the freq again, etc..