Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758846AbYLSWMq (ORCPT ); Fri, 19 Dec 2008 17:12:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756584AbYLSWGO (ORCPT ); Fri, 19 Dec 2008 17:06:14 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:54264 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756666AbYLSWGM (ORCPT ); Fri, 19 Dec 2008 17:06:12 -0500 Date: Fri, 19 Dec 2008 23:05:56 +0100 From: Ingo Molnar To: Steven Rostedt Cc: =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Pekka J Enberg , linux-kernel@vger.kernel.org, Pekka Paalanen , Markus Metzger Subject: Re: [PATCH] ftrace: introduce tracing_reset_online_cpus() helper Message-ID: <20081219220556.GK2351@elte.hu> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1664 Lines: 44 * Steven Rostedt wrote: > > On Fri, 19 Dec 2008, Fr?d?ric Weisbecker wrote: > > > > > > That's looks good. > > By the past, I also suggested Steven to automatically reset the traces > > buffer each time a tracer is started, that > > would factor out the code a bit more. I don't think one tracer would > > avoid to reset the buffer once it is started, and > > I don't think it is needed to reset twice on tracer switching: on stop > > of the old tracer and on start on the new. Only > > on start should be enough. > > I'm actually against the idea of reseting a trace everytime we enable it. > That is: > > echo 1 > /debug/tracing/tracing_enabled > > This should not reset the tracer. I actually do tracing where I disable > and enable it around areas I am interested in. I want all tracing, not > just the last one. > > Now we have recently added /debug/tracing/tracing_on which can quickly > stop tracing. I may be able to use that, and we can let the > tracing_enable" reset it too. > > I'll have to take a look at my scripts to see if that would work. yep, using /debug/tracing/tracing_enabled is the right model to quickly toggle tracing without losing the buffer. The 'switch tracer' op is really a slow thing anyway. It can involve unpatching/repatching functions, etc. etc. - and while it works, it shouldnt really be encouraged as a dynamic tool coding pattern. 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/