From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754920AbZI3R7G (ORCPT ); Wed, 30 Sep 2009 13:59:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754202AbZI3R7F (ORCPT ); Wed, 30 Sep 2009 13:59:05 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:61970 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752361AbZI3R7F (ORCPT ); Wed, 30 Sep 2009 13:59:05 -0400 Subject: Re: 2.6.31.1 boot crash, compiled with ftrace From: Steven Rostedt To: Dick Hollenbeck Cc: linux-kernel@vger.kernel.org, Peter Zijlstra In-Reply-To: <4AC371C6.3050104@softplc.com> References: <4AC22613.4090803@softplc.com> <1254297804.2963.14.camel@frodo> <1254301761.7286.4.camel@frodo> <4AC371C6.3050104@softplc.com> Content-Type: text/plain Date: Wed, 30 Sep 2009 13:57:36 -0400 Message-Id: <1254333456.2194.27.camel@frodo> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2009-09-30 at 09:57 -0500, Dick Hollenbeck wrote: > My real pursuit here is to find the reason for a nearly 1 second latency > when running a SCHED_RR userspace process. The filesystem is ext3 off > the flash card via IDE. Linux is yanking the machine away from this > process sporadically for up to 1 second, no disk file calls in this > proces, only some serial port and networking (epoll) userspace calls in > a loop. It is insane. So I have to get either LTT or FTRACE enabled, > never used either before. Its been a tough 2 weeks. Just getting the > LTT patches in sync with a decent kernel has been nearly unbearable. > Great to hear that you narrowed it down. BTW, if you want to learn some more about ftrace, I just gave a 2 hour tutorial at LinuxCon last week. You can download the slides in the link below. They show lots of samples. I'll also start writing a howto for LWN real soon. So if you don't already have a subscription, I suggest you get one ;-) http://people.redhat.com/srostedt/ftrace-tutorial-linux-con-2009.odp -- Steve