From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751078AbWGKQBb (ORCPT ); Tue, 11 Jul 2006 12:01:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751025AbWGKQBb (ORCPT ); Tue, 11 Jul 2006 12:01:31 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:11907 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1751075AbWGKQBa (ORCPT ); Tue, 11 Jul 2006 12:01:30 -0400 Subject: Re: [discuss] Re: [PATCH] Allow all Opteron processors to change pstate at same time From: Arjan van de Ven To: Alan Cox Cc: Andi Kleen , Joachim Deguara , Mark Langsdorf , discuss@x86-64.org, linux-kernel@vger.kernel.org, cpufreq@lists.linux.org.uk In-Reply-To: <1152634538.18028.23.camel@localhost.localdomain> References: <1152622554.4489.32.camel@lapdog.site> <200607111507.39079.ak@suse.de> <1152623675.3128.41.camel@laptopd505.fenrus.org> <1152634538.18028.23.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 11 Jul 2006 18:01:23 +0200 Message-Id: <1152633683.3128.84.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2006-07-11 at 17:15 +0100, Alan Cox wrote: > Ar Maw, 2006-07-11 am 15:14 +0200, ysgrifennodd Arjan van de Ven: > > if you have per cpu offset and speed, then you don't even need to tie > > all frequencies together... sounds like the best solution to me.. > > CPU clocks on some systems are not stable relative to one another. Doing > the maths only works if you know the divergence isn't cause by > independant clock sources obviously you do math only on your local cpu, with the values for your local cpu. And just never ever look at tsc values from another cpu, consider them entirely uncorrelated for all I care ;) Within those constraints it should be reasonably ok (there still is trouble if the tsc stops entirely in idle, but thats a different thing)