From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965013AbVHOWSv (ORCPT ); Mon, 15 Aug 2005 18:18:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965014AbVHOWSv (ORCPT ); Mon, 15 Aug 2005 18:18:51 -0400 Received: from e34.co.us.ibm.com ([32.97.110.132]:38326 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S965015AbVHOWSu (ORCPT ); Mon, 15 Aug 2005 18:18:50 -0400 Subject: Re: [PATCH] pmtmr and PRINTK_TIME timings display From: john stultz To: Borislav Petkov Cc: Steven Rostedt , lkml In-Reply-To: <200508041723.25848.petkov@uni-muenster.de> References: <200508041459.43500.petkov@uni-muenster.de> <1123161545.12009.6.camel@localhost.localdomain> <200508041723.25848.petkov@uni-muenster.de> Content-Type: text/plain Date: Mon, 15 Aug 2005 15:18:46 -0700 Message-Id: <1124144326.8630.9.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2005-08-04 at 17:23 +0200, Borislav Petkov wrote: > I get it. Actually, I wasn't very sure whether this is the right solution > since my desktop machine uses tsc timer as default while the laptop the > pmtmr. I also remember that there was a patch a while ago on lkml which > enabled a modifiable behavior for PRINTK_TIME through a /proc interface and > kernel boot option but it somehow didn't get accepted. Ok, then, since we > keep the jiffies solution across arch's, how can I force the kernel to use > tsc for printk timings so that i can see the deltas between the different > printk's instead of the jiffies_64 ns value? The Pentium-M Centrino on the > laptop evidently supports rdtsc as a msr instruction. The issue is that there are a number of laptops that do not properly support cpufreq and additionally newer laptop chips halt their TSC's when they go into C3 mode. This keeps the TSC from working as a proper timesource on these systems, and causes the need for alternative timesources like the ACPI PM timer. thanks -john