From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762534AbYEHKlO (ORCPT ); Thu, 8 May 2008 06:41:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756477AbYEHKk6 (ORCPT ); Thu, 8 May 2008 06:40:58 -0400 Received: from mail.gmx.net ([213.165.64.20]:36229 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1756163AbYEHKk5 (ORCPT ); Thu, 8 May 2008 06:40:57 -0400 X-Authenticated: #34473864 X-Provags-ID: V01U2FsdGVkX18oTIkWQsUokKMDFjMrKQsMESmn6e/WyjHXNroUTH niUpyxwjP9hjDu Message-ID: <4822D8B6.4090008@gmx.de> Date: Thu, 08 May 2008 12:40:54 +0200 From: Philipp Kohlbecher User-Agent: Thunderbird 2.0.0.14 (X11/20080505) MIME-Version: 1.0 To: linux-kernel@vger.kernel.org CC: Thomas Gleixner , John Stultz Subject: clocksources: order of preference Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Why is the TSC preferred to the HPET as a clocksource for the x86 architecture? "Understanding the Linux Kernel" states that the HPET is preferable to the TSC due to its richer architecture. Up to version 2.6.17.14, arch/i386/kernel/timers/timer.c also contained a comment to that effect and accordingly ranked the HPET before the TSC. This was changed when the new clocksource infrastructure was introduced with version 2.6.18. (The HPET clocksource received a rating of 250; the TSC, 300.) Preferring the TSC leads to problems when it is unstable. While this can be prevented by setting CONFIG_X86_TSC, certain distribution kernels (striving for compatibility) don't, resulting in soft lockups. Are there better reasons to prefer the TSC or may I submit a patch that swaps the respective ratings? Thanks for reading, - Philipp Kohlbecher Please CC me, I am not on the list.