From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752193Ab2A3KLd (ORCPT ); Mon, 30 Jan 2012 05:11:33 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:58327 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751576Ab2A3KLb (ORCPT ); Mon, 30 Jan 2012 05:11:31 -0500 Date: Mon, 30 Jan 2012 11:11:21 +0100 From: Ingo Molnar To: Peter Zijlstra , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker Cc: Andrew Steets , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Mackerras , Arnaldo Carvalho de Melo Subject: Re: perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect Message-ID: <20120130101121.GB8924@elte.hu> References: <4F22D8D9.3010108@rgmadvisors.com> <20120128120151.GA10390@elte.hu> <4F248938.5030507@rgmadvisors.com> <20120129163235.GB23408@elte.hu> <1327917156.2446.191.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1327917156.2446.191.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes 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 * Peter Zijlstra wrote: > On Sun, 2012-01-29 at 17:32 +0100, Ingo Molnar wrote: > > * Andrew Steets wrote: > > > > > On 1/28/12 6:01 AM, Ingo Molnar wrote: > > > > > > >> prctl(PR_TASK_PERF_EVENTS_DISABLE) doesn't appear to > > > >> disable perf event counters. Here is a demonstration > > > >> program: > > > > > > > > btw., what's your usecase? > > > > > > I'm trying to profile a small section of a long-running > > > program. I ran into trouble using call-graph recording > > > and I thought this might be an alternative way of getting > > > what I was after. > > > > That usecase indeed makes sense. Peter, could we allow this > > for privileged tasks, depending on the perf_paranoia > > settings or such? > > I really dislike it. The sane way around this would be to > allow easy self-profiling instead of doing things arse about > face like that. So, what workflow are you suggesting to Andrew? I guess we are also hurting from the lack of dwarf stack backtrace decoding - that would allow the filtering by parent function without modifying the code. I think Frederic had a prototype working for 32-bit - any update on that? Andrew could work that problem around right now by adding: -fno-omit-frame-pointer to the build of the utility - that should activate -g and perf-report's --parent filter should also work fine. Thanks, Ingo