Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965389AbWIRFDN (ORCPT ); Mon, 18 Sep 2006 01:03:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965387AbWIRFDN (ORCPT ); Mon, 18 Sep 2006 01:03:13 -0400 Received: from tomts25-srv.bellnexxia.net ([209.226.175.188]:60577 "EHLO tomts25-srv.bellnexxia.net") by vger.kernel.org with ESMTP id S965388AbWIRFDM (ORCPT ); Mon, 18 Sep 2006 01:03:12 -0400 Date: Mon, 18 Sep 2006 01:03:10 -0400 From: Mathieu Desnoyers To: Ingo Molnar Cc: Karim Yaghmour , Theodore Tso , Nicholas Miell , Paul Mundt , linux-kernel , Ingo Molnar , Jes Sorensen , Andrew Morton , Roman Zippel , Tom Zanussi , Richard J Moore , "Frank Ch. Eigler" , Michel Dagenais , Christoph Hellwig , Greg Kroah-Hartman , Thomas Gleixner , William Cohen , "Martin J. Bligh" Subject: LTTng and SystemTAP (Everyone who is scared to read this huge thread, skip to here) Message-ID: <20060918050310.GC15930@Krystal> References: <20060917143623.GB15534@elte.hu> <1158524390.2471.49.camel@entropy> <20060917230623.GD8791@elte.hu> <450DEEA5.7080808@opersys.com> <20060918005624.GA30835@elte.hu> <450DFFC8.5080005@opersys.com> <20060918033027.GB11894@elte.hu> <20060918035216.GF9049@thunk.org> <450E1F6F.7040401@opersys.com> <20060918043248.GB19843@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20060918043248.GB19843@elte.hu> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.4.32-grsec (i686) X-Uptime: 00:50:18 up 26 days, 1:59, 2 users, load average: 0.45, 0.36, 0.29 User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2175 Lines: 45 * Ingo Molnar (mingo@elte.hu) wrote: > so regarding the big picture we are largely on the same page in essence > i think - sub-issues non-withstanding :-) As long as LTT comes with a > facility that allows the painless moving of a static LTT markup to a > SystemTap script, that would come quite a bit closer to being acceptable > for upstream acceptance in my opinion. > > The curious bit is: why doesnt LTT integrate SystemTap yet? Is it the > performance aspect? Yes, for our needs, the performance impact of SystemTAP is too high. We are totally open to integrate data coming from SystemTAP to our traces. Correct me if I am wrong, but I think their project does an extensive use of strings in the buffers. This is one, non compact, sub-optimal type, but it can do the job for low rate events. I also makes classification and identification of the information rather less straightforward. Plus, running a string format code in a critical code path does not give the kind of performance I am looking for. > Some of the extensive hooking you do in LTT could be > aleviated to a great degree if you used dynamic probes. For example the > syscall entry hackery in LTT looks truly scary. Yes, agreed. The last time I checked, I thought about moving this tracing code to the syscall_trace_entry/exit (used for security hooks and ptrace if I remember well). I just didn't have the time to do it yet. > I cannot understand that > someone who does tracing doesnt see the fundamental strength of > SystemTap - i think that in part must have lead to my mistake of > assuming that you opposed SystemTap. > Can you find a way to instrument it dynamically without the breakpoint cost ? System calls are a highly critical path both in a system and for tracing. Mathieu OpenPGP public key: http://krystal.dyndns.org:8080/key/compudj.gpg Key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - 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/