Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932249AbXFFLxR (ORCPT ); Wed, 6 Jun 2007 07:53:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761673AbXFFLxG (ORCPT ); Wed, 6 Jun 2007 07:53:06 -0400 Received: from 207.47.60.4.static.nextweb.net ([207.47.60.4]:62382 "EHLO rpc.xensource.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751861AbXFFLxF (ORCPT ); Wed, 6 Jun 2007 07:53:05 -0400 User-Agent: Microsoft-Entourage/11.3.3.061214 Date: Wed, 06 Jun 2007 12:52:59 +0100 Subject: Re: [Xen-devel] [patch 14/33] xen: xen time implementation From: Keir Fraser To: Jan Beulich CC: Jeremy Fitzhardinge , Xen-devel , Andrew Morton , Andi Kleen , lkml , Chris Wright , , Ingo Molnar , Linus Torvalds , Thomas Gleixner Message-ID: Thread-Topic: [Xen-devel] [patch 14/33] xen: xen time implementation Thread-Index: AceoMTpmeRN5yhQkEdyEZAAX8io7RQ== In-Reply-To: <4666AFEF.76E4.0078.0@novell.com> Mime-version: 1.0 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1108 Lines: 27 On 6/6/07 12:00, "Jan Beulich" wrote: >> If the error across CPUS is +/- just a few microseconds at worst then having >> the clocksource clamp to no less than the last timestamp returned seems a >> reasonable fix. Time won't 'stop' for longer than the cross-CPU error, and >> that should always be a tiny value. > > Are you sure this is also true when e.g. a CPU gets throttled due to thermal > conditions? It is my understanding that both the duty cycle adjustment and > the frequency reduction would yield a reduced rate TSC, which would be > accounted for only the next time the local clock gets calibrated. Otherwise, > immediate calibration (and vcpu update) would need to be forced out of the > thermal interrupt. Yes, this could be an issue. Is there any way to get an interrupt or MCE when thermal throttling occurs? -- Keir - 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/