From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261580AbTJHSXS (ORCPT ); Wed, 8 Oct 2003 14:23:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261639AbTJHSXS (ORCPT ); Wed, 8 Oct 2003 14:23:18 -0400 Received: from pentafluge.infradead.org ([213.86.99.235]:25987 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S261580AbTJHSXR (ORCPT ); Wed, 8 Oct 2003 14:23:17 -0400 Subject: Re: Time precision, adjtime(x) vs. gettimeofday From: Benjamin Herrenschmidt To: Gabriel Paubert Cc: linuxppc-dev list , Linux Kernel list In-Reply-To: <20031008175059.GA31743@iram.es> References: <1065619951.25818.15.camel@gaston> <20031008154846.GA29868@iram.es> <1065630178.26943.54.camel@gaston> <20031008175059.GA31743@iram.es> Content-Type: text/plain Message-Id: <1065637323.897.12.camel@gaston> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.5 Date: Wed, 08 Oct 2003 20:22:04 +0200 Content-Transfer-Encoding: 7bit X-SA-Exim-Mail-From: benh@kernel.crashing.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Pentafluge-Mail-From: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > I repeat the question: what are the values of drift on the machines > that encounter the problem ? Is this drift stable or unstable? So far, there is no problem. The problem that was happening was a via_calibrate_decr() bug with HZ != 100, but when investigating, I figured out that we had a potential problem there, that's all and that's why I want people like you who know those problems well to state if it's worth bothering ;) > > > > On all cases, those will drift some way from what the NTP server will > > give, either a lot or not, it will. So we may end up adjusting our > > kernel rate and thus opening a window for the problem. > > The worst variations of drift I've seen are a few ppm for a given > machine, barring the occasional boot-time calibration problems that > I have encountered. OK.