From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753224AbeBEPHx (ORCPT ); Mon, 5 Feb 2018 10:07:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:53182 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753134AbeBEPHr (ORCPT ); Mon, 5 Feb 2018 10:07:47 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF5E92075D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Mon, 5 Feb 2018 10:07:43 -0500 From: Steven Rostedt To: Juri Lelli Cc: Alexei Starovoitov , Mathieu Desnoyers , linux-kernel , Linus Torvalds , Ingo Molnar , Andrew Morton , Thomas Gleixner , Peter Zijlstra , Masami Hiramatsu , Tom Zanussi , linux-rt-users , linux-trace-users , acme , Clark Williams , Jiri Olsa , bristot , Jonathan Corbet , Namhyung Kim , Dietmar Eggemann , Patrick Bellasi , Morten Rasmussen Subject: Re: [PATCH 00/18] [ANNOUNCE] Dynamically created function based events Message-ID: <20180205100743.4420c0e6@gandalf.local.home> In-Reply-To: <20180205135355.GX19535@localhost.localdomain> References: <20180202230458.840252014@goodmis.org> <261141691.15507.1517677454208.JavaMail.zimbra@efficios.com> <20180203140217.2382df69@gandalf.local.home> <20180203205207.mpob4w6eyehhg2ky@ast-mbp> <20180203161732.4a65c66b@gandalf.local.home> <20180205135355.GX19535@localhost.localdomain> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 5 Feb 2018 14:53:55 +0100 Juri Lelli wrote: > First impression is that this is going to be definitely useful if > > - it's possibile to hook at function end (e.g., replenish_dl_entity above > carries more useful information _after_ it did its job) The one issue is that you will only have access to one argument at the end. And that will be the return value. How useful would that be? Hmm, actually, if we incorporate Tom Zanussi's histogram patches (which I'll start reviewing this week for inclusion), we could add the pseudo events to carry necessary data. > - inside functions? not really sure it's actually going to be needed, but I > was wondering if it's possible at all :); with tracepoints it's for example > easy to collect detailed information about which branches has been taken etc. This will not be something to handle anything other than function calls. You have three options for dealing with inside a function. - add another function that can be traced with this, inside the function - use kprobes - add a tracepoint > > I'm going to play with this more. Just wanted to give back a quick positive > feedback. Thanks! > > I'm also adding Arm folks to the discussion, as they (and I :) have been > asking to add tracepoints to scheduler code in the past [1]. You will need to implement the arch_get_func_args() for ARM too. -- Steve