From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753041AbYFAORE (ORCPT ); Sun, 1 Jun 2008 10:17:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751762AbYFAOQu (ORCPT ); Sun, 1 Jun 2008 10:16:50 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:4363 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751333AbYFAOQu (ORCPT ); Sun, 1 Jun 2008 10:16:50 -0400 Date: Sat, 31 May 2008 23:13:06 +0200 From: Pavel Machek To: Arjan van de Ven Cc: Vaidyanathan Srinivasan , Linux Kernel , venkatesh.pallipadi@intel.com, suresh.b.siddha@intel.com, Michael Neuling , Balbir Singh , "Amit K. Arora" Subject: Re: [RFC PATCH v1 0/3] Scaled statistics using APERF/MPERF in x86 Message-ID: <20080531211306.GM5405@ucw.cz> References: <20080526142513.24680.97164.stgit@drishya.in.ibm.com> <20080526085000.33787eac@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080526085000.33787eac@infradead.org> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > entitlement for the process as per the current CPU frequency. This > > technique is used in powerpc architecture with the help of hardware > > registers that accurately capture the entitlement. > > > > there are some issues with this unfortunately, and these make it > a very complex thing to do. > Just to mention a few: > 1) What if the BIOS no longer allows us to go to the max frequency for > a period (for example as a result of overheating); with the approach > above, the admin would THINK he can go faster, but he cannot in reality, > so there's misleading information (the system looks half busy, while in Plus time one-second-computation-job returning anything else is just wrong. Even when it only happens when overheated... or only on battery power. If you want scaled utime, you need new interface. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html