From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756761AbZBRVPp (ORCPT ); Wed, 18 Feb 2009 16:15:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752491AbZBRVPh (ORCPT ); Wed, 18 Feb 2009 16:15:37 -0500 Received: from casper.infradead.org ([85.118.1.10]:37639 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752287AbZBRVPg (ORCPT ); Wed, 18 Feb 2009 16:15:36 -0500 Subject: Re: [PATCH] new irq tracer From: Peter Zijlstra To: Jason Baron Cc: mingo@elte.hu, rostedt@goodmis.org, linux-kernel@vger.kernel.org, acme@ghostprotocols.net, fweisbec@gmail.com, fche@redhat.com, compudj@krystal.dyndns.org In-Reply-To: <20090218195328.GA3112@redhat.com> References: <20090218195328.GA3112@redhat.com> Content-Type: text/plain Date: Wed, 18 Feb 2009 22:15:25 +0100 Message-Id: <1234991725.4799.1.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.25.91 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2009-02-18 at 14:53 -0500, Jason Baron wrote: > hi, > > Using a copule of tracepoints i've implemented an 'irq tracer' which has > the following column format: > > [time][irq][action][handled][cpu][length] > > for example on my system: > > [ 1038.927248381] 28 eth0 1 3 0.000002745 > [ 1038.927544688] 28 eth0 1 3 0.000002520 > [ 1038.927593609] 28 eth0 1 3 0.000002509 > [ 1038.974087675] 29 ahci 1 1 0.000013135 > [ 1038.974288475] 29 ahci 1 1 0.000005542 > [ 1038.974414324] 29 ahci 1 1 0.000007953 > > I think this patch is useful in understanding irq system behavior, and > for tracking down irq driver handlers that are firing too often or > spending too much time handling an irq. This approach could be extended > to the timer irq and for softirqs... The function graph tracer can already do this, it has a special section to recognize irq entry function, and already measures time spend. I guess with Steve's new triggers (probes or whatever they ended up being called) you could limit it to just IRQ entry points.