Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751527Ab0ALFI7 (ORCPT ); Tue, 12 Jan 2010 00:08:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751116Ab0ALFI5 (ORCPT ); Tue, 12 Jan 2010 00:08:57 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:37001 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751036Ab0ALFI4 (ORCPT ); Tue, 12 Jan 2010 00:08:56 -0500 X-Authority-Analysis: v=1.0 c=1 a=g2MyM69NJrgA:10 a=7U3hwN5JcxgA:10 a=dSoPn6ytcG0D-0lOLHAA:9 a=FhOLUdBU3Uo-cgZvbh8A:7 a=UQUmolc5_3_zeSOV1qycMPWZzeUA:4 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.89.75 Subject: Re: [RFC] [PATCH 7/7] Ftrace plugin for Uprobes From: Steven Rostedt Reply-To: rostedt@goodmis.org To: Frederic Weisbecker Cc: Srikar Dronamraju , Ingo Molnar , Arnaldo Carvalho de Melo , Peter Zijlstra , Ananth N Mavinakayanahalli , utrace-devel , Jim Keniston , Masami Hiramatsu , Maneesh Soni , Mark Wielaard , LKML In-Reply-To: <20100112045454.GJ5243@nowhere> References: <20100111122521.22050.3654.sendpatchset@srikar.in.ibm.com> <20100111122608.22050.94088.sendpatchset@srikar.in.ibm.com> <20100112045454.GJ5243@nowhere> Content-Type: text/plain; charset="ISO-8859-15" Organization: Kihon Technologies Inc. Date: Tue, 12 Jan 2010 00:08:53 -0500 Message-ID: <1263272933.28171.3804.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1546 Lines: 50 On Tue, 2010-01-12 at 05:54 +0100, Frederic Weisbecker wrote: > Now what if I want to launch ls and want to profile a function > inside. What can I do with a trace event. I can't create the > probe event based on a pid as I don't know it in advance. > I could give it the ls cmdline and it manages to activate > on the next ls launched. This is racy as another ls can > be launched concurrently. You make a wrapper script: #!/bin/sh $$ exec $* I do this all the time to limit the function tracer to a specific app. #!/bin/sh echo $$ > /debug/tracing/set_ftrace_pid echo function > /debug/tracing/current_tracer exec $* The exec will cause the ls to have the pid of $$. -- Steve > > So I can only say there that an ftrace plugin or an ftrace trace > event would be only a half-useful interface to exploit utrace > possibilities because it only lets us trace already running > apps. Moreover I bet the most chosen workflow to profile/trace > uprobes is by launching an app and profile it from the beginning, > not by profiling an already running one, which makes an ftrace > interface even less than half useful there. > > ftrace is cool to trace the kernel, but this kind of tricky > userspace tracing workflow is not adapted to it. > > What do you think? > -- 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/