Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755068AbZJTGoB (ORCPT ); Tue, 20 Oct 2009 02:44:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754883AbZJTGoA (ORCPT ); Tue, 20 Oct 2009 02:44:00 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:50168 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754716AbZJTGoA (ORCPT ); Tue, 20 Oct 2009 02:44:00 -0400 Date: Tue, 20 Oct 2009 08:43:34 +0200 From: Ingo Molnar To: Frederic Weisbecker Cc: Masami Hiramatsu , Steven Rostedt , lkml , Thomas Gleixner , Arnaldo Carvalho de Melo , Mike Galbraith , Paul Mackerras , Peter Zijlstra , Christoph Hellwig , Ananth N Mavinakayanahalli , Jim Keniston , "Frank Ch. Eigler" , "H. Peter Anvin" , systemtap , DLE Subject: Re: [PATCH -tip tracing/kprobes 0/9] tracing/kprobes, perf: perf probe and kprobe-tracer bugfixes Message-ID: <20091020064334.GK8550@elte.hu> References: <20091017000711.16556.69935.stgit@dhcp-100-2-132.bos.redhat.com> <20091017080203.GA4155@elte.hu> <20091017103427.GA31238@elte.hu> <4ADAAF50.9040604@redhat.com> <20091019075103.GF17960@elte.hu> <20091019110055.GA5549@nowhere> <20091019112125.GA12829@elte.hu> <20091019193248.GB4880@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091019193248.GB4880@nowhere> User-Agent: Mutt/1.5.19 (2009-01-05) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2036 Lines: 46 * Frederic Weisbecker wrote: [...] > > I think absolute and relative line modes are not colliding/contending > at all but actually fit two different needs. Definitely so. > - absolute is nice when you are lonely doing kernel debugging. > (can be expanded at will once you imagine user probes) > You are stuck in your code editor, trying to figure out the > origin of your problem and then you think it would be nice > to set a probe in branch 1 and in branch 2 inside func_foo(). > Then you already have absolute lines and relying in > perf probe --list func_foo() to resolve an absolute line into > a relative one is a very undesired middle step. Of course - absolute numbers definitely rule for everything that works on a whole-file basis. (I'd argue that if you do that from an editor then you want a short macro that just sets a probe there - much like a breakpoint. Such an editor macro would want to use absolute numbers.)) > - relative is nice in some other cases. When you already have > the function target in mind, you even don't need to check your > editor, just a quick check to this command and get the relative > line. But also when you want to transmit a probe reference > in a mailing list because of its better lifetime. also useful for command line workflows: 'perf probe --list' output - i think we users to generate func_symbol+rel_position kind of probes. Plus a relative position is more intuitive as well. If you see 'schedule+10' versus 'schedule+102', you'll know it immediate that the first one is early in the function while the second one is near the end. If you see 'schedule@2465' versus 'schedule@2555' that kind of 'where in the function is the probe, roughly' subjective impression is lost. Ingo -- 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/