Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751294AbWIPKSp (ORCPT ); Sat, 16 Sep 2006 06:18:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751321AbWIPKSp (ORCPT ); Sat, 16 Sep 2006 06:18:45 -0400 Received: from omx2-ext.sgi.com ([192.48.171.19]:5537 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S1751294AbWIPKSo (ORCPT ); Sat, 16 Sep 2006 06:18:44 -0400 Message-ID: <450BCF97.3000901@sgi.com> Date: Sat, 16 Sep 2006 12:19:03 +0200 From: Jes Sorensen User-Agent: Thunderbird 1.5.0.5 (X11/20060907) MIME-Version: 1.0 To: Andrew Morton Cc: Ingo Molnar , tglx@linutronix.de, karim@opersys.com, Paul Mundt , Roman Zippel , Mathieu Desnoyers , linux-kernel@vger.kernel.org, Christoph Hellwig , Ingo Molnar , Greg Kroah-Hartman , Tom Zanussi , ltt-dev@shafik.org, Michel Dagenais Subject: Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108 References: <20060915132052.GA7843@localhost.usen.ad.jp> <20060915135709.GB8723@localhost.usen.ad.jp> <450AB5F9.8040501@opersys.com> <450AB506.30802@sgi.com> <450AB957.2050206@opersys.com> <20060915142836.GA9288@localhost.usen.ad.jp> <450ABE08.2060107@opersys.com> <1158332447.5724.423.camel@localhost.localdomain> <20060915111644.c857b2cf.akpm@osdl.org> <20060915181907.GB17581@elte.hu> <20060915131317.aaadf568.akpm@osdl.org> In-Reply-To: <20060915131317.aaadf568.akpm@osdl.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2376 Lines: 51 Andrew Morton wrote: > On Fri, 15 Sep 2006 20:19:07 +0200 > Ingo Molnar wrote: > >> * Andrew Morton wrote: >> >>> What Karim is sharing with us here (yet again) is the real in-field >>> experience of real users (ie: not kernel developers). >> well, Jes has that experience and Thomas too. > > systemtap and ltt are the only full-scale tracing tools which target > sysadmins and applciation developers of which I am aware.. Just to clarify, the stuff I have looked at in the field was based on LTT, but not part of the official LTT. It simply goes to show that end users cannot agree on a small set of fixed tracepoints because someone always wants a slightly different view of things, like in the cases I looked at. Not to mention that the changes LTT users make, at times, to shoehorn their stuff in, especially in sensitive codepaths such as the syscall path, have side effects which clearly weren't considered. In one case I ended up doing an alternative implementation using kprobes to prove that similar results could be achieved in that manner. Strangely enough I was right :) I don't have any objections to markers as Ingo suggested. I just don't buy the repeated argument that LTT has been around for years and barely changed. It's simply a case of the LTT team not being aware (or deciding to ignore, I cannot say which) what users have actually done with the LTT codebase, but it seems obvious they are not aware what everyone is doing with it. But we have seen before how if an infrastructure like LTT goes into the kernel, many more users will pop up and want to have their stuff added. The other part is the constantly repeated performance claim, which to this point hasn't been backed up by any hard evidence. If we are to take that argument serious, then I strongly encourage the LTT community to present some real numbers, but until then it can be classified as nothing but FUD. I shall be the first to point out that kprobes are less than ideal, especially the current ia64 implementation suffers from some tricky limitations, but thats an implementation issue. Cheers, Jes - 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/