Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262116AbVBAUon (ORCPT ); Tue, 1 Feb 2005 15:44:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262120AbVBAUon (ORCPT ); Tue, 1 Feb 2005 15:44:43 -0500 Received: from mx2.elte.hu ([157.181.151.9]:4517 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S262116AbVBAUoP (ORCPT ); Tue, 1 Feb 2005 15:44:15 -0500 Date: Tue, 1 Feb 2005 21:44:00 +0100 From: Ingo Molnar To: Lee Revell Cc: Tom Rini , Bill Huey , linux-kernel@vger.kernel.org, Rui Nuno Capela , Mark_H_Johnson@Raytheon.com, "K.R. Foley" , Adam Heath , Florian Schmidt , Thomas Gleixner , Fernando Pablo Lopez-Lezcano , Steven Rostedt Subject: Re: [patch] Real-Time Preemption, -RT-2.6.11-rc2-V0.7.36-04 Message-ID: <20050201204359.GA346@elte.hu> References: <20041207132927.GA4846@elte.hu> <20041207141123.GA12025@elte.hu> <20041214132834.GA32390@elte.hu> <20050104064013.GA19528@nietzsche.lynx.com> <20050104094518.GA13868@elte.hu> <20050107192651.GG5259@smtp.west.cox.net> <20050126080952.GC4771@elte.hu> <1107288076.18349.7.camel@krustophenia.net> <20050201201704.GA32139@elte.hu> <1107289878.18349.20.camel@krustophenia.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1107289878.18349.20.camel@krustophenia.net> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2095 Lines: 58 * Lee Revell wrote: > OK. So for application triggered tracing you need LATENCY_TRACING > enabled, as described here: > > http://lkml.org/lkml/2004/10/29/312 correct, that too should still work fine - with the small change that there's now a separate flag to active it: echo 1 > /proc/sys/kernel/trace_user_triggered # default: 0 it is an orthogonal mechanism to atomicity-debugging. since i wrote the above mail 3 months ago, a number of improvements have been done to the tracer. There are a handful of modifier feature-flags to the tracer, which can be used to get additional functionality. Here's a quick summary: echo 1 > /proc/sys/kernel/trace_freerunning # default: 0 will get a 'freerunning' tracer which never stops (and overwrites the oldest entries if the trace gets full). Especially with long latencies this in some cases can be more informative. this flag: echo 0 > /proc/sys/kernel/mcount_enabled # default: 1 causes the tracer to record only key kernel events (schedule/wakeup events, etc.), not every kernel function call. This might be useful if you want to see the bigger picture and want to validate scheduling logic on a bigger scale, spanning a much longer timeframe. and if you have stability problems, this flag might be handy: echo 1 > /proc/sys/kernel/trace_freerunning # default: 0 it will dump the current kernel trace to the kernel console if a crash happens - obviously only useful with a serial console or netconsole. It's a big dump but can make some bugs much easier to debug. on SMP: echo 1 > /proc/sys/kernel/trace_all_cpus # default: 0 this flag will cause all activity from all CPUs to be included in the trace. This can be useful if it is suspected that a particular latency was caused not by the CPU where the latency triggers, but by some other CPU. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/