From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964839AbcATKZY (ORCPT ); Wed, 20 Jan 2016 05:25:24 -0500 Received: from foss.arm.com ([217.140.101.70]:44381 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932979AbcATKZV (ORCPT ); Wed, 20 Jan 2016 05:25:21 -0500 Date: Wed, 20 Jan 2016 10:25:48 +0000 From: Juri Lelli To: Mark Brown Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, vincent.guittot@linaro.org, robh+dt@kernel.org, mark.rutland@arm.com, linux@arm.linux.org.uk, sudeep.holla@arm.com, lorenzo.pieralisi@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, morten.rasmussen@arm.com, dietmar.eggemann@arm.com Subject: Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems Message-ID: <20160120102548.GO8573@e106622-lin> References: <1452262172-31861-1-git-send-email-juri.lelli@arm.com> <20160119150551.GI6344@twins.programming.kicks-ass.net> <20160119175038.GS6588@sirena.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160119175038.GS6588@sirena.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/01/16 17:50, Mark Brown wrote: > On Tue, Jan 19, 2016 at 04:05:51PM +0100, Peter Zijlstra wrote: > > On Fri, Jan 08, 2016 at 02:09:28PM +0000, Juri Lelli wrote: > > > > cons: - not easy to come up with a clean solution, as it seems interaction > > > with several subsystems (e.g., cpufreq) is required > > > - not easy to agree upon a single benchmark (that has to be both > > > representative and simple enough to run at boot) > > > - numbers might (and do) vary from boot to boot > > > This last point is a total pain for benchmarking, it means nothing is > > every reproducible. > > > Therefore, I would always augment the above (2) with the below (3), such > > that you can overwrite the results with a known stable set of numbers: > > The suggestion when the previous version was being discussed was that > there are supposed to be some other knobs one uses for tuning and one > was never supposed to use these numbers. Right, DT solution might live without a sysfs interface, as you want to use those other knobs for runtime tuning. Dynamic solution instead, and I think this is what Peter was also pointing out, will most probably require a sysfs interface for cases in which variation of default values from boot to boot is not acceptable. From mboxrd@z Thu Jan 1 00:00:00 1970 From: juri.lelli@arm.com (Juri Lelli) Date: Wed, 20 Jan 2016 10:25:48 +0000 Subject: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems In-Reply-To: <20160119175038.GS6588@sirena.org.uk> References: <1452262172-31861-1-git-send-email-juri.lelli@arm.com> <20160119150551.GI6344@twins.programming.kicks-ass.net> <20160119175038.GS6588@sirena.org.uk> Message-ID: <20160120102548.GO8573@e106622-lin> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 19/01/16 17:50, Mark Brown wrote: > On Tue, Jan 19, 2016 at 04:05:51PM +0100, Peter Zijlstra wrote: > > On Fri, Jan 08, 2016 at 02:09:28PM +0000, Juri Lelli wrote: > > > > cons: - not easy to come up with a clean solution, as it seems interaction > > > with several subsystems (e.g., cpufreq) is required > > > - not easy to agree upon a single benchmark (that has to be both > > > representative and simple enough to run at boot) > > > - numbers might (and do) vary from boot to boot > > > This last point is a total pain for benchmarking, it means nothing is > > every reproducible. > > > Therefore, I would always augment the above (2) with the below (3), such > > that you can overwrite the results with a known stable set of numbers: > > The suggestion when the previous version was being discussed was that > there are supposed to be some other knobs one uses for tuning and one > was never supposed to use these numbers. Right, DT solution might live without a sysfs interface, as you want to use those other knobs for runtime tuning. Dynamic solution instead, and I think this is what Peter was also pointing out, will most probably require a sysfs interface for cases in which variation of default values from boot to boot is not acceptable.