Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965583AbcCJK4a (ORCPT ); Thu, 10 Mar 2016 05:56:30 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:33387 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754067AbcCJK4U (ORCPT ); Thu, 10 Mar 2016 05:56:20 -0500 Date: Thu, 10 Mar 2016 11:56:14 +0100 From: Peter Zijlstra To: Vincent Guittot Cc: Juri Lelli , mturquette , Linux PM list , Ingo Molnar , Srinivas Pandruvada , "Rafael J. Wysocki" , Viresh Kumar , "Rafael J. Wysocki" , Linux Kernel Mailing List , Steve Muckle , ACPI Devel Maling List Subject: Re: [PATCH 6/6] cpufreq: schedutil: New governor based on scheduler utilization data Message-ID: <20160310105614.GK6375@twins.programming.kicks-ass.net> References: <20160308112759.GF6356@twins.programming.kicks-ass.net> <20160308192640.GD6344@twins.programming.kicks-ass.net> <20160309163930.GP6356@twins.programming.kicks-ass.net> <20160310100728.GT6344@twins.programming.kicks-ass.net> <20160310103008.GU6344@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160310103008.GU6344@twins.programming.kicks-ass.net> 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: 1382 Lines: 40 On Thu, Mar 10, 2016 at 11:30:08AM +0100, Peter Zijlstra wrote: > On Thu, Mar 10, 2016 at 05:23:54PM +0700, Vincent Guittot wrote: > > > > No, since its a compile time thing, we can simply do: > > > > > > #ifdef arch_scale_freq_capacity > > > next_freq = (1 + 1/n) * max_freq * (util / max) > > > #else > > > next_freq = (1 + 1/n) * current_freq * (util_raw / max) > > > #endif > > > > selecting formula at compilation is clearly better. I wrongly thought that > > it can't be accepted as a solution. > > Well, its bound to get more 'interesting' since I forse implementations > not always actually doing the invariant thing. > > Take for example the thing I send: > > lkml.kernel.org/r/20160303162829.GB6375@twins.programming.kicks-ass.net > > it both shows why you cannot talk about current_freq but also that the > above needs a little more help (for the !X86_FEATURE_APERFMPERF case). > > But the !arch_scale_freq_capacity case should indeed be that simple. Maybe something like: #ifdef arch_scale_freq_capacity #ifndef arch_scale_freq_invariant #define arch_scale_freq_invariant() (true) #endif #else /* arch_scale_freq_capacity */ #define arch_scale_freq_invariant() (false) #endif if (arch_scale_freq_invariant()) And have archs that have conditional arch_scale_freq_capacity() implementation provide a arch_scale_freq_invariant implementation.