Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933867Ab0KQNhR (ORCPT ); Wed, 17 Nov 2010 08:37:17 -0500 Received: from canuck.infradead.org ([134.117.69.58]:39964 "EHLO canuck.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757404Ab0KQNhQ convert rfc822-to-8bit (ORCPT ); Wed, 17 Nov 2010 08:37:16 -0500 Subject: Re: [ANNOUNCE] New utility: 'trace' From: Peter Zijlstra To: Ingo Molnar Cc: Frederic Weisbecker , Darren Hart , Thomas Gleixner , LKML , Linus Torvalds , Andrew Morton , Steven Rostedt , Arjan van de Ven , Arnaldo Carvalho de Melo , Masami Hiramatsu , Tom Zanussi , Mathieu Desnoyers , Li Zefan , Jason Baron , "David S. Miller" , Christoph Hellwig , Pekka Enberg , Lai Jiangshan , Eric Dumazet In-Reply-To: <20101117131023.GE27063@elte.hu> References: <4CE2F747.4060406@linux.intel.com> <20101116221726.GB26243@nowhere> <20101117083020.GA11336@elte.hu> <1289993750.2109.718.camel@laptop> <20101117125344.GC5464@nowhere> <1289998957.2109.751.camel@laptop> <20101117131023.GE27063@elte.hu> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 17 Nov 2010 14:36:16 +0100 Message-ID: <1290000976.2109.782.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2722 Lines: 56 On Wed, 2010-11-17 at 14:10 +0100, Ingo Molnar wrote: > * Peter Zijlstra wrote: > > > On Wed, 2010-11-17 at 13:53 +0100, Frederic Weisbecker wrote: > > > On Wed, Nov 17, 2010 at 12:35:50PM +0100, Peter Zijlstra wrote: > > > > On Wed, 2010-11-17 at 09:30 +0100, Ingo Molnar wrote: > > > > > > For example I'm currently working with dozens of trace_printk() and I would be > > > > > > very happy to turn some of them off half of the time. > > > > > > > > > > I guess we could try such a patch. If you send a prototype i'd be interested in > > > > > testing it out. > > > > > > > > I don't see the point, the kernel shouldn't contain any trace_printk()s > > > > to begin with.. > > > > > > > > > It's oriented toward developers. Those who use dozens of tracepoints in > > > their tree because they are debugging something or developing a new feature, > > > they might to deactivate/reactivate some of these independant points. > > > > > > This can also apply to dynamic_printk of course. > > > > > > Well, the very first and main point is to standardize trace_printk into > > > a trace event so that it gets usable by perf tools. I have been asked many > > > times "how to use trace_printk() with perf?". > > > > Thing is, since its these dev who add the trace_printk()s to begin with, I don't > > see the point in splitting them out, if you didn't want them why did you add them > > to begin with?! > > That's a common workflow: lots of printks (trace_printk's) put all around the code - > and sometimes one set of tracepoints is needed, one time another set. > > _If_ we succeed in presenting them like Frederic suggested it, and if we make the > turning on/off _simpler_ (no kernel modification) and faster (no kernel reboot) via > the tooling, people like Frederic might start using it. > > I dont think we should fight the workflow itself - it makes sense. > > The only question is whether we can represent it all in a nicer fashion than 'modify > the source code and reboot'. If we cannot then there's no point - but i'm not sure > about it and Frederic seems to be convinced too that he can make such a switch > on/off facility intuitive. We'll only see if we try it. > > Also, i dont see any harm - do you? Yes, trace_printk() is a pure debug interface, solely meant for the edit + reboot cycle. If you want anything more than that we've got tracepoints. The rule up until now has been to never merge a trace_printk() user. -- 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/