Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756733Ab3DWVCt (ORCPT ); Tue, 23 Apr 2013 17:02:49 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:53892 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753892Ab3DWVCr (ORCPT ); Tue, 23 Apr 2013 17:02:47 -0400 Date: Tue, 23 Apr 2013 14:01:56 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Christoph Lameter , Frederic Weisbecker , Ingo Molnar , LKML , Chris Metcalf , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , Kevin Hilman , Li Zhong , Oleg Nesterov , Paul Gortmaker , Peter Zijlstra , Thomas Gleixner Subject: Re: [PATCH 2/2] nohz: Add basic tracing Message-ID: <20130423210156.GD3427@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1366664905-21884-1-git-send-email-fweisbec@gmail.com> <1366664905-21884-3-git-send-email-fweisbec@gmail.com> <0000013e38188092-7e0b72ea-9ae0-417c-902a-5e8a88282073-000000@email.amazonses.com> <1366747223.9609.163.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1366747223.9609.163.camel@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13042321-2876-0000-0000-000007D6D94A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1339 Lines: 40 On Tue, Apr 23, 2013 at 04:00:23PM -0400, Steven Rostedt wrote: > On Tue, 2013-04-23 at 18:12 +0000, Christoph Lameter wrote: > > On Mon, 22 Apr 2013, Frederic Weisbecker wrote: > > > > > It's not obvious to find out why the full dynticks subsystem > > > doesn't always stop the tick: whether this is due to kthreads, > > > posix timers, perf events, etc... > > > > > > These new tracepoints are here to help the user diagnose > > > the failures and test this feature. > > > > Very good. This will help a lot. > > You can also do: > > cd /sys/kernel/debug/tracing > echo 1 > max_graph_depth > echo function_graph > current_tracer > > And then run your code, and look to see what happens on the cpu in > question: > > cat per_cpu/cpuX/trace > > The "max_graph_depth" of one will make the function graph tracer just > trace the first function that enters the kernel. You'll be able to see > if the kernel did anything to your userspace application that wasn't > planned. > > "max_graph_depth" was added in 3.9-rc1 Very cool! I have added this to the documentation. Thanx, Paul -- 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/