From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756876AbZINTeH (ORCPT ); Mon, 14 Sep 2009 15:34:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756856AbZINTeG (ORCPT ); Mon, 14 Sep 2009 15:34:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21278 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756855AbZINTeF (ORCPT ); Mon, 14 Sep 2009 15:34:05 -0400 Message-ID: <4AAE9B41.3020905@redhat.com> Date: Mon, 14 Sep 2009 15:36:33 -0400 From: Masami Hiramatsu User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Thunderbird/3.0b3 MIME-Version: 1.0 To: Frederic Weisbecker CC: Steven Rostedt , Ingo Molnar , lkml , systemtap , DLE , Jim Keniston , Ananth N Mavinakayanahalli , Andi Kleen , Christoph Hellwig , "Frank Ch. Eigler" , "H. Peter Anvin" , Jason Baron , "K.Prasad" , Lai Jiangshan , Li Zefan , Peter Zijlstra , Srikar Dronamraju , Tom Zanussi Subject: Re: [PATCH tracing/kprobes 4/7] tracing/kprobes: Add event profiling support References: <20090910235258.22412.29317.stgit@dhcp-100-2-132.bos.redhat.com> <20090910235329.22412.94731.stgit@dhcp-100-2-132.bos.redhat.com> <20090911031253.GD16396@nowhere> <4AAA7938.7070200@redhat.com> <20090914030244.GC14306@nowhere> <4AAE7540.9090009@redhat.com> <20090914185540.GD6045@nowhere> In-Reply-To: <20090914185540.GD6045@nowhere> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Frederic Weisbecker wrote: > On Mon, Sep 14, 2009 at 12:54:24PM -0400, Masami Hiramatsu wrote: >>>> I'd like to have a dispatcher function and flags internally :) >>> >>> >>> You mean kprobes that could support multiple probes? >>> That would be a nice solution IMHO... >> >> Yeah, actually kprobes could support multiple probes on the >> same point. But kprobe structure has many extensions which >> kprobe-tracer doesn't need, e.g. post_handler/break_handler, >> opcode, arch sprcific instructions. >> Kretprobe consumes more memories for storing return points :(. >> >> Thus, if we know there are two functions to be called on the >> same probe point, I think it is better to have a dispatcher. >> (Especially, in this case, we can call fixed functions, so >> it's easier way.) > > > Yeah, you could union the post_handler with profile_handler > or something like that. No, you can't do that, because kprobes calls post_handler if it is not NULL. > > It depends if kprobes may need one day to support an undeterminate > number of probes. Kprobes itself is supporting those multiple kprobes on the same address. I meant that we don't need to have multiple kprobes on the same "kprobe-tracer's event". Even if introducing a dispatcher, kprobe-tracer can support multiple trace-event at the same location. > Also, is the post_handler called at the same location than the normal > probe? No, post_handler is called after single-stepping. > And is a post handler called even if there is no normal handler? Yes, it is. Hmm, I assume I have told about kprobes infrastructure, and have you told about kprobe-tracer?:) > There might be some of such factors that would force you to handle a > lot of corner cases, things that you wouldn't need to worry about > if you just had to maintain a simple rcu list of probes to call. Anyway, I never see who are using post_handler:). I'm not sure why it is needed... -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@redhat.com