From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: [ltt-dev] Fw: [PATCH] ext4: Add markers for better debuggability Date: Sat, 10 Jan 2009 11:19:06 -0500 Message-ID: <20090110161906.GB20526@Krystal> References: <20090109170408.75C1.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20090109144901.GA7262@Krystal> <20090109185840.GD23869@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: KOSAKI Motohiro , ltt-dev@lists.casi.polymtl.ca, Ext4 Developers List , linux-kernel@vger.kernel.org, Ingo Molnar , Steven Rostedt To: Theodore Tso Return-path: Received: from tomts36-srv.bellnexxia.net ([209.226.175.93]:54173 "EHLO tomts36-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751976AbZAJQTI (ORCPT ); Sat, 10 Jan 2009 11:19:08 -0500 Content-Disposition: inline In-Reply-To: <20090109185840.GD23869@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: * Theodore Tso (tytso@mit.edu) wrote: > On Fri, Jan 09, 2009 at 09:49:01AM -0500, Mathieu Desnoyers wrote: > > > > Given this is meant to be in the mainline kernel, using tracepoints > > rather than markers would be more appropriate. Please see > > Documentation/tracepoints.txt and samples/tracepoints/ for details. > > I saw that, but I'm still not sure how I would actually *use* > tracepoints. I can use markers today with Systemtap, and I need an > easy way to be able to selectively do things like "trap and print all > of the logged data when the ext4_request_inode tracepoint/marker is > tripped where dev=='dm-8'". > > Unfortunately, Systemtap seems doomed given its current course and > direction, so I'm not opposed to moving to another solution --- I just > need a HOWTO that demonstrates how I can do this painlessly and > easily; preferably without having me have to manually hack up a kernel > module each time I want to implement the tracing > > Is there an easy way to do that using ltt today? Can you point me at > a sample of how this could be done? > Hi Ted, I just ported LTTng to 2.6.28 yesterday and started doing the port of ext4/jbd2 to tracepoints. As you can see in my 0.74 announcement, the tracepoint work for both jbd2 and ext4 is done. I also did the lttng probe module for jbd2. Now I just have to create the probe module for ext4. I also want to create debugfs files to control per-probe module filtering, e.g. : /mnt/debugfs/ltt/filter/jbd2/dev /mnt/debugfs/ltt/filter/ext4/dev Where writing to it would add device names to the filter list. I would like a scheme where we can easily add/remove devices, list all devices... I think ftrace already has something similar for instrumentation activation. The main question I am facing is : What interface semantic do we want for such filter control file ? Comments/ideas are welcome. Mathieu > - Ted > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68