From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753012AbYKXMVP (ORCPT ); Mon, 24 Nov 2008 07:21:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752081AbYKXMU7 (ORCPT ); Mon, 24 Nov 2008 07:20:59 -0500 Received: from tomts43.bellnexxia.net ([209.226.175.110]:60911 "EHLO tomts43-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751205AbYKXMU6 (ORCPT ); Mon, 24 Nov 2008 07:20:58 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AswEAN8oKklMROB9/2dsb2JhbACBbc5Cgnw Date: Mon, 24 Nov 2008 07:20:55 -0500 From: Mathieu Desnoyers To: Christoph Hellwig Cc: ltt-dev@lists.casi.polymtl.ca, Zhaolei , Lai Jiangshan , Ingo Molnar , Steven Rostedt , linux-kernel@vger.kernel.org, Thomas Gleixner , Linus Torvalds , Andrew Morton , Sam Ravnborg Subject: Re: LTTng kernel integration roadmap, update Message-ID: <20081124122055.GA18626@Krystal> References: <20081124112842.GA15615@Krystal> <20081124114124.GA32459@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20081124114124.GA32459@infradead.org> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 07:08:44 up 7 days, 12:49, 4 users, load average: 1.13, 0.93, 0.69 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Christoph Hellwig (hch@infradead.org) wrote: > On Mon, Nov 24, 2008 at 06:28:42AM -0500, Mathieu Desnoyers wrote: > > - trimmed-down lttv for the kernel tree > > Need to look at > > git://git.kernel.org/pub/scm/linux/kernel/git/sam/test.git#master > > tests/ directory, which permits building userspace tools with the > > Linux kernel. I recently got the idea of populating debugfs with > > userspace tools that would sits in kernel module data. How (in)sane > > does this idea look ? That would seems like a rather good solution to > > ship the userspace tool with the kernel. > > Completely insane I'd say. Debugfs is per defintion populated from > kernelspace, and adding another mixed user/kernel populated fs like > devfs is a rather bad idea. I don't quite see any point in shipping > lttv with the kernel tree either, it shouldn't really need knowledge of > the kernel version. > The key idea behind this is to answer to Thomas Gleixner concerns, who supports that a tracer should output data in text-format only so it can be used with tools kernel developers have on their system, like "cat". However, getting data out of the kernel efficiently simply cannot be done with such approach. Therefore, LTTng needs its own userspace tools to splice the data out of the kernel efficiently. Another tool is used to pretty-print the binary data into text. Then the problem becomes : we have to make the userspace tool easy enough to deploy so even Linus can find and use it. ;) But indeed, the trace buffers are versioned, so if the format changes between kernel versions, the userspace tools will detect it and the user will know it must update its tools. So it's not really a problem there. The question that prevails is therefore : should we ship userspace binary with the kernel tree at all ? And if yes, how should the resuting executables be packaged and deployed ? Should it be installed in the system along with kernel modules or should it be populated into a filesystem populated by kernelspace ? Or is it better to do as we have always done and keep the userspace tools separated from the kernel tree ? Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68