From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755794AbcBVV0v (ORCPT ); Mon, 22 Feb 2016 16:26:51 -0500 Received: from mail-lb0-f181.google.com ([209.85.217.181]:35929 "EHLO mail-lb0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755500AbcBVV0t (ORCPT ); Mon, 22 Feb 2016 16:26:49 -0500 MIME-Version: 1.0 In-Reply-To: <20160222093244.GB27380@e106622-lin> References: <3071836.JbNxX8hU6x@vostro.rjw.lan> <20160219080917.GE22643@pablo> <5324745.ObXn8lTQ9A@vostro.rjw.lan> <20160222093244.GB27380@e106622-lin> Date: Mon, 22 Feb 2016 22:26:47 +0100 X-Google-Sender-Auth: QejKpcQhQ-nLf3JfhjWBoFmdTlQ Message-ID: Subject: Re: [PATCH v10 1/3] cpufreq: Add mechanism for registering utilization update callbacks From: "Rafael J. Wysocki" To: Juri Lelli Cc: "Rafael J. Wysocki" , "Rafael J. Wysocki" , Linux PM list , Peter Zijlstra , Ingo Molnar , Linux Kernel Mailing List , Srinivas Pandruvada , Viresh Kumar , Steve Muckle , Thomas Gleixner Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 22, 2016 at 10:32 AM, Juri Lelli wrote: > On 19/02/16 23:14, Rafael J. Wysocki wrote: >> On Friday, February 19, 2016 08:09:17 AM Juri Lelli wrote: >> > Hi Rafael, >> > >> > On 18/02/16 21:22, Rafael J. Wysocki wrote: >> > > On Mon, Feb 15, 2016 at 10:47 PM, Rafael J. Wysocki wrote: >> > > > From: Rafael J. Wysocki >> > > > [cut] >> That said, if the concern is that there are plans to change the way the >> scheduler computes the utilization numbers and that may become difficult to >> carry out if cpufreq starts to depend on them in their current form, then I >> may agree that it is valid, but I'm not aware of those plans ATM. >> > > No, I don't think there's any substantial discussion going on about the > utilization numbers. OK, so the statement below applies. >> However, if the numbers are going to stay what they are, I don't see why >> passing them to cpufreq may possibly become problematic at any point. > > My concern was mostly on the fact that there is already another RFC > under discussion that uses the same numbers and has different hooks > placed in scheduler code (Steve's sched-freq); so, additional hooks > might generate confusion, IMHO. So this is about the hooks rather than about their arguments after all, isn't it? I fail to see why it is better to drop the arguments and leave the hooks, then. OTOH, I see reasons for keeping the arguments along with the hooks, but let me address that in my next reply. Now, if the call sites of the hooks change in the future, it won't be a problem for me as long as the new hooks are invoked on a regular basis or, if they aren't, as long as I can figure out from the arguments they pass that I should not expect an update any time soon. If the arguments change, it won't be a problem either as long as they are sufficient to be inserted into the frequency selection formula used by the schedutil governor I posted and produce sensible frequencies for the CPU. Thanks, Rafael