From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754842Ab0CEUkm (ORCPT ); Fri, 5 Mar 2010 15:40:42 -0500 Received: from ksp.mff.cuni.cz ([195.113.26.206]:50376 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754725Ab0CEUkh (ORCPT ); Fri, 5 Mar 2010 15:40:37 -0500 Date: Fri, 5 Mar 2010 21:40:29 +0100 From: Pavel Machek To: "Pallipadi, Venkatesh" Cc: Randy Dunlap , Ingo Molnar , H Peter Anvin , Thomas Gleixner , Len Brown , Dave Jones , "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" Subject: Re: [patch 2/2] x86: Manage ENERGY_PERF_BIAS based on cpufreq governor Message-ID: <20100305204029.GB20554@elf.ucw.cz> References: <20100303000649.757684000@intel.com> <20100303000849.278509000@intel.com> <4B8DADB9.1040302@xenotime.net> <20100303215453.GG2579@ucw.cz> <1267662469.16916.1020.camel@localhost.localdomain> <20100305091949.GA31554@atrey.karlin.mff.cuni.cz> <7C53B33EE871F14797C999838AA8B5A914ACD58C@orsmsx505.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7C53B33EE871F14797C999838AA8B5A914ACD58C@orsmsx505.amr.corp.intel.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > >You should say what the setting does; you can mention below what MSR > >it corresponds to, but "Control IA32_ENERGY_PERF_BIAS setting" is not > >suitable user documentation. > > > >> Also, the expectation here is that kernel will do the right thing by > >> default. The option here is to the user who_knows_what_he_is_doing to > >> override the kernel default. > > > >You did not give user enough information to do anything intelligent... > > I have rephrased it in the newer version sent yday with more info. Good. > >> > Also... does it make change to tweak the setting during > >runtime? Maybe > >> > different settings for AC and battery power? > >> > >> Yes. Matthew mentioned in other response aboue setting this based on > >> freq. For the CPUs that support this feature currently, we don't see > >> advantage in setting this feature at run time. > > > >If the feature is useless, then why set it at all? > > I just said changing it at run time doesn't give us benefits. Not >that That can be only true if it does not give benefits period... AC and battery power are quite different scenarios. > the feature is useless. Having the default value for the tunable in > mid-range does increase energy-efficiency than the tunable being > at performance level. So... what does it really do? What is the difference in power consumption, and what is the difference in performance? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html