From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760033AbZBZWbt (ORCPT ); Thu, 26 Feb 2009 17:31:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755647AbZBZWba (ORCPT ); Thu, 26 Feb 2009 17:31:30 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:40650 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755361AbZBZWb3 (ORCPT ); Thu, 26 Feb 2009 17:31:29 -0500 Subject: Re: Linux 2.6.29-rc6 From: john stultz To: Thomas Gleixner Cc: Jesper Krogh , Linus Torvalds , Linux Kernel Mailing List , Len Brown In-Reply-To: References: <49A6F39F.9040801@krogh.cc> <49A6FEE2.90700@krogh.cc> <1f1b08da0902261319k7a60d80xaafc1101facfd2d9@mail.gmail.com> <49A70B24.6090706@krogh.cc> <1235685269.6811.11.camel@localhost.localdomain> Content-Type: text/plain Date: Thu, 26 Feb 2009 14:31:23 -0800 Message-Id: <1235687483.6811.26.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2009-02-26 at 23:06 +0100, Thomas Gleixner wrote: > On Thu, 26 Feb 2009, john stultz wrote: > > On Thu, 2009-02-26 at 22:35 +0100, Jesper Krogh wrote: > > > > Also mind sending the full dmesg for both kernels? > > > > > > http://krogh.cc/~jesper/dmesg-2.6.29-rc6.txt > > > http://krogh.cc/~jesper/dmesg-2.6.26.8.txt > > > > So one interesting difference: > > 2.6.26.8: TSC calibrated against PM_TIMER > > 2.6.29-rc6: Fast TSC calibration using PIT > > > > Thomas, any thoughts as to why we might be calibrating off the PIT > > instead of the PM_TIMER w/ 2.6.29? > > Yup, because we introduced the Fast PIT calibration in 2.6.28. Ah. Ok. > 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. I wouldn't think so. Although, I'm recalling on some systems here right after we deploy them we'll see something similar to the originally reported ntpd "time reset" noise for a period of time while ntpd tries to find the right freq. For some reason, I've noticed, having multiple servers in your ntp.conf seems to increase NTP's difficulty at picking a time and converging. So this may be just the slight calibration change is confusing ntp or it may be the NTP_INTERVAL_LENGTH change from awhile back which would cause the drift value to change could be doing the same thing (although I thought that landed in the 2.6.24 timeframe, but I may be forgetting). I'll kick up some of my own testing between these two releases to see if I can't find something similar. Jesper: How long was the box up for when you noticed the ntpd noise? Also what's the output of the following under the different kernels: ntpdc -c peers ntpdc -c kerninfo thanks -john