Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755260AbXJ2Wz6 (ORCPT ); Mon, 29 Oct 2007 18:55:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752221AbXJ2Wzu (ORCPT ); Mon, 29 Oct 2007 18:55:50 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:49845 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865AbXJ2Wzu (ORCPT ); Mon, 29 Oct 2007 18:55:50 -0400 Date: Mon, 29 Oct 2007 23:55:28 +0100 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: Zachary Amsden , Glauber de Oliveira Costa , linux-kernel@vger.kernel.org, tglx@linutronix.de, rusty@rustcorp.com.au, --cc@redhat.com, avi@quramnet.com, kvm-devel@lists.sourceforge.net, Glauber de Oliveira Costa , Dan Hecht , Garrett Smith Subject: Re: [PATCH] raise tsc clocksource rating Message-ID: <20071029225528.GA31293@elte.hu> References: <11936994092607-git-send-email-gcosta@redhat.com> <1193697734.9793.86.camel@bodhitayantram.eng.vmware.com> <20071029224852.GA27547@elte.hu> <47266431.1010500@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47266431.1010500@goop.org> User-Agent: Mutt/1.5.16 (2007-06-09) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0002] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 797 Lines: 20 * Jeremy Fitzhardinge wrote: > > if it's inaccurate why are you exposing it to the guest then? Native > > only uses the TSC if it's safe and accurate to do so. > > It is used as part of the Xen clocksource as a short term > extrapolator, with correction parameters supplied by the hypervisor. > It should never be used directly. that's totally broken then. You cannot create an SMP-safe monotonic clocksource via interpolation - native does not do it either. Good thing this problem got exposed, it needs to be fixed. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/