Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934095Ab0KQNnK (ORCPT ); Wed, 17 Nov 2010 08:43:10 -0500 Received: from mail-bw0-f46.google.com ([209.85.214.46]:56541 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751444Ab0KQNnI (ORCPT ); Wed, 17 Nov 2010 08:43:08 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=kkobjLE9pmTkQigxE62ryc4s2I+dpwwEKn1C/s3O2Qjhi4W9EbaGllcfBpbOnqXEOd rLQSTo+ocLogXQPN/z6ZTcvGd61lrz+yvIrO1Hgvq9Sm4zkIXY3Od4LVCjo3GfIcI78W 89Ec6GqziGy37pq7q0jfTpDLtoXJdTxvDf+aI= Date: Wed, 17 Nov 2010 14:43:02 +0100 From: Frederic Weisbecker To: Peter Zijlstra Cc: Ingo Molnar , 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 Subject: Re: [ANNOUNCE] New utility: 'trace' Message-ID: <20101117134300.GG5464@nowhere> 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> <1290000976.2109.782.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1290000976.2109.782.camel@laptop> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3113 Lines: 65 On Wed, Nov 17, 2010 at 02:36:16PM +0100, Peter Zijlstra wrote: > 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. So why prevent from making it even more handy? > 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. Sure, that doesn't change the core idea of trace_prink(): none of them must be merged. That new event interface would just make private uses of trace_printk() more convenient. -- 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/