From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759367AbZEHP1W (ORCPT ); Fri, 8 May 2009 11:27:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754854AbZEHP1J (ORCPT ); Fri, 8 May 2009 11:27:09 -0400 Received: from science.horizon.com ([192.35.100.1]:19687 "HELO science.horizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753705AbZEHP1I (ORCPT ); Fri, 8 May 2009 11:27:08 -0400 Date: 8 May 2009 11:27:06 -0400 Message-ID: <20090508152706.17300.qmail@science.horizon.com> From: "George Spelvin" To: johnstul@us.ibm.com, linux@horizon.com Subject: Re: [RFC][PATCH] tsc_khz= boot option to avoid TSC calibration variance Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, tglx@linutronix.de, ulrich.windl@rz.uni-regensburg.de, williams@redhat.com, zippel@linux-m68k.org In-Reply-To: <20090508121913.9039.qmail@science.horizon.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > I'd suggest the following: I should add the documentation patch that goes with it: diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 90b3924..6747881 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2391,10 +2391,20 @@ and is between 256 and 4096 characters. It is defined in the file tsc= Disable clocksource-must-verify flag for TSC. Format: - [x86] reliable: mark tsc clocksource as reliable, this - disables clocksource verification at runtime. - Used to enable high-resolution timer mode on older - hardware, and in virtualized environment. + [x86] if value is "reliable", mark tsc clocksource + as reliable. This disables clocksource verification + at runtime. Used to enable high-resolution timer mode + on older hardware, and in virtualized environment. + + tsc_khz= [x86] Set the TSC freq value. + Format: + Used to avoid TSC calibration error. The TSC frequency + is re-measured each boot, and changes by a few parts + per hundred thousand each time. This is noticeable to + time synchronization applications like NTP. + This option makes it consistent across boots. + If the specified value differs from the measured one + by more than 0.1%, it is ignored. turbografx.map[2|3]= [HW,JOY] TurboGraFX parallel port interface