From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750860AbXBFMia (ORCPT ); Tue, 6 Feb 2007 07:38:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751753AbXBFMia (ORCPT ); Tue, 6 Feb 2007 07:38:30 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:56629 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750860AbXBFMi3 (ORCPT ); Tue, 6 Feb 2007 07:38:29 -0500 Date: Tue, 6 Feb 2007 13:37:16 +0100 From: Ingo Molnar To: John Cc: linux-kernel@vger.kernel.org, tglx@timesys.com, johnstul@us.ibm.com, akpm@osdl.org Subject: Re: One-shot high-resolution POSIX timer periodically late Message-ID: <20070206123716.GA8481@elte.hu> References: <45C1BE5C.9050001@free.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45C1BE5C.9050001@free.fr> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.3 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.3 required=5.9 tests=ALL_TRUSTED,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 1.0 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.4950] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * John wrote: > > 2.6.18-rt7 is pretty old, do you see the problem in 2.6.20-rc6-rt5 > > too? > > Ingo, Thomas, > > I cannot reproduce in 2.6.20-rc6-rt6, but it is not strictly an > apples-to-apples comparison because I get a tsc clocksource in > 2.6.20-rc6-rt6, and an acpi_pm clocksource in 2.6.18.6-rt7. that suggests that the TSC was not deemed reliable by the newer kernel - which almost always means it's not realiable. I think the problems you were seeing are consistent with TSC being non-monotonic - so the fix is to not use the TSC - and the newer kernel does this automatically. Ingo