From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756856AbZBZWZO (ORCPT ); Thu, 26 Feb 2009 17:25:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757263AbZBZWYz (ORCPT ); Thu, 26 Feb 2009 17:24:55 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:58347 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757340AbZBZWYy (ORCPT ); Thu, 26 Feb 2009 17:24:54 -0500 Date: Thu, 26 Feb 2009 14:24:25 -0800 (PST) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Thomas Gleixner cc: john stultz , Jesper Krogh , Linux Kernel Mailing List , Len Brown Subject: Re: Linux 2.6.29-rc6 In-Reply-To: Message-ID: References: <49A6F39F.9040801@krogh.cc> <49A6FEE2.90700@krogh.cc> <1f1b08da0902261319k7a60d80xaafc1101facfd2d9@mail.gmail.com> <49A70B24.6090706@krogh.cc> <1235685269.6811.11.camel@localhost.localdomain> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 26 Feb 2009, Thomas Gleixner wrote: > > Is the delta anything NTP might get upset about: > > 2.6.26: time.c: Detected 2311.847 MHz processor. > 2.6.29: Detected 2310.029 MHz processor. > > If yes, then we need to fix NTP not the calibration code :) Well, that _is_ about 500ppm difference, and we claim that we _should_ have reached 150ppm with the 15ms delay. We clearly don't seem to have done that. I'm not quite sure why - we _should_ be finding the edge of the PIT events to within roughly a microsecond (assuming that's about as long as an "inb" takes), and that should give us a pretty good fast calibration, but maybe I'm overlooking something. Or - and this may be more likely - there are chipsets that aren't very good at reading the PIT in a tight loop. That may explain why it's a problem on Jesper's hardware, but we haven't gotten tons of reports of this from others. I see that it's a SunFire X2200, which I think uses an nVidia HT southbridge. I assume it's an nForce4 thing. There shouldn't be anything odd there, and the PIT read shouldn't be taking any longer than on anything else, but who knows? Linus