From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756202AbZCJTnQ (ORCPT ); Tue, 10 Mar 2009 15:43:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753305AbZCJTm6 (ORCPT ); Tue, 10 Mar 2009 15:42:58 -0400 Received: from 2605ds1-ynoe.1.fullrate.dk ([90.184.12.24]:36143 "EHLO shrek.krogh.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753049AbZCJTm5 (ORCPT ); Tue, 10 Mar 2009 15:42:57 -0400 Message-ID: <49B6C2B8.7000407@krogh.cc> Date: Tue, 10 Mar 2009 20:42:48 +0100 From: Jesper Krogh User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Thomas Gleixner CC: Linus Torvalds , john stultz , Linux Kernel Mailing List , Len Brown Subject: Re: Linux 2.6.29-rc6 References: <49A6F39F.9040801@krogh.cc> <49A6FEE2.90700@krogh.cc> <1f1b08da0902261319k7a60d80xaafc1101facfd2d9@mail.gmail.com> <49A70B24.6090706@krogh.cc> <1235685269.6811.11.camel@localhost.localdomain> <1235687483.6811.26.camel@localhost.localdomain> <49A78C79.304@krogh.cc> <1235766936.7402.5.camel@localhost.localdomain> <49ACC853.8070205@krogh.cc> <1236110026.6068.18.camel@localhost> <49AD90E2.7050209@krogh.cc> <1236118969.6068.87.camel@localhost> <49AE9EA4.2080500@krogh.cc> <49AECA3B.5030503@krogh.cc> <1236193075.3793.63.camel@jstultz-laptop> <1236220759.6863.7.camel@localhost.localdomain> <1236221530.6863.9.camel@localhost.localdomain> <49B57F3D.5030008@krogh.cc> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thomas Gleixner wrote: > On Mon, 9 Mar 2009, Linus Torvalds wrote: >> On Mon, 9 Mar 2009, Jesper Krogh wrote: >>> First boot. >>> [ 0.000000] ref_freq: 2311825 pit_freq: 2310386 >>> Second boot: >>> [ 0.000000] ref_freq: 2311803 pit_freq: 2310190 >>> Third boot: >>> [ 0.000000] ref_freq: 2311824 pit_freq: 2310080 >>> Fourth boot: >>> [ 0.000000] ref_freq: 2311831 pit_freq: 2310130 >> It's really quite impressively stable, but the fast-PIT calibration >> frequency is reliably about 3/4 of a promille low. Or, put another way, >> the TSC difference over the pit calibration is just a _tad_ too small >> compared to the value we'd expect if that loop of pit_expect_msb() would >> really run at the expected delay of a 1.193182MHz clock divided by 256. >> >> And it's stable in that it really always seems to be off by a very similar >> amount. It's not moving around very much. >> >> I also wonder why it seems to happen mainly just to _you_. There's >> absolutely nothing odd in your system, neither a slow CPU or anything >> else that would stand out. >> >> Grr. Very annoyingly non-obvious. > > Indeed. One hint is in the slow calibration path. 3 of 4 boots have: > >>> [ 0.000000] TSC: PIT calibration matches PMTIMER. 2 loops > > So the slow calibration path detects some disturbance. > > Jesper, can you please apply the following patch instead of Johns and > provide the output for a couple of boots? The output is: > > Fast TSC calibration using PIT > tsc 43425305 tscmin 624008 tscmax 632610 First boot: [ 0.000000] Fast TSC calibration using PIT [ 0.000000] tsc 34202223 tscmin 474069 tscmax 500664 Second boot: Here I didnt get above messages.. http://krogh.cc/~jesper/dmesg-boot2.txt Third boot: [ 0.000000] Fast TSC calibration using PIT [ 0.000000] tsc 34199856 tscmin 470321 tscmax 502182 Forth boot: [ 0.000000] Fast TSC calibration using PIT [ 0.000000] tsc 34202008 tscmin 475510 tscmax 501501 The second one is really strange.. is'nt it? While booting up I saw this one on the serial console.. root@quad12:~# hwclock --systohc Cannot access the Hardware Clock via any known method. Use the --debug option to see the details of our search for an access method. root@quad12:~# hwclock --systohc --debug hwclock from util-linux-ng 2.13.1 hwclock: Open of /dev/rtc failed, errno=2: No such file or directory. No usable clock interface found. Cannot access the Hardware Clock via any known method. Jesper -- Jesper