From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755952AbXGIO2R (ORCPT ); Mon, 9 Jul 2007 10:28:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751862AbXGIO2F (ORCPT ); Mon, 9 Jul 2007 10:28:05 -0400 Received: from ik-out-1112.google.com ([66.249.90.178]:17920 "EHLO ik-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751315AbXGIO2C (ORCPT ); Mon, 9 Jul 2007 10:28:02 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=XT3hGMGFihthIu+zZNtoT97/mDDGKUqg/DAzoSfL2VmBn3crZ/ng3x3I6/VE2QnJvDYg86ZDqGaodNY0QTS3gv/Poi/vZCjhAPZ98qRrNlxy5LLOv3oP1zFGoP8z1C6ixQ1ifAYCaBYRTwmLY5OKVmNbZozW1OeEY1SzDy5V4Es= Message-ID: <5a4c581d0707090727q15eff62ax1fdb1271754cc2d2@mail.gmail.com> Date: Mon, 9 Jul 2007 16:27:59 +0200 From: "Alessandro Suardi" To: "Linux Kernel Mailing List" Subject: clocksource change of behavior in 2.6.22 compared to 2.6.20 causes massive system clock slowdown MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org My oldish AMD K7-800's clock began falling behind after rebooting from 2.6.20 (and 109 days uptime with a spotless clock) into 2.6.22; time lost is about four minutes each hour. Turns out that 2.6.22 marks my TSC as unstable and starts using PIT instead. Rebooting 2.6.22 with clocksource=tsc gets the original stable system time back. Not sure whether this is supposed to be the default way of fixing the issue on older machines, though; if anyone sees a problem with this, I'm up for providing more information. [root@donkey ~]# cd /sys/devices/system/clocksource/clocksource0/ [root@donkey clocksource0]# cat available_clocksource pit jiffies tsc [root@donkey clocksource0]# cat current_clocksource tsc [root@donkey clocksource0]# uname -a Linux donkey 2.6.22 #1 PREEMPT Mon Jul 9 13:26:38 CEST 2007 i686 athlon i386 GNU/Linux [root@donkey clocksource0]# cat /proc/cpuinfo processor : 0 vendor_id : AuthenticAMD cpu family : 6 model : 4 model name : AMD Athlon(tm) Processor stepping : 2 cpu MHz : 800.068 cache size : 256 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr syscall mmxext 3dnowext 3dnow bogomips : 1603.17 clflush size : 32 thanks, ciao, --alessandro "Did you get married but forgot to get divorced ?" (Danny and Dusty, 'The Good Old Days')