Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752840Ab3EJJ3a (ORCPT ); Fri, 10 May 2013 05:29:30 -0400 Received: from merlin.infradead.org ([205.233.59.134]:37340 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751714Ab3EJJ33 (ORCPT ); Fri, 10 May 2013 05:29:29 -0400 Date: Fri, 10 May 2013 11:27:41 +0200 From: Peter Zijlstra To: Jiri Olsa Cc: linux-kernel@vger.kernel.org, Corey Ashford , Frederic Weisbecker , Ingo Molnar , Namhyung Kim , Paul Mackerras , Arnaldo Carvalho de Melo , Andi Kleen , David Ahern , Stephane Eranian Subject: Re: [PATCH 0/9] perf: Adding better precise_ip field handling Message-ID: <20130510092741.GE3039@dyad.programming.kicks-ass.net> References: <1368106344-23383-1-git-send-email-jolsa@redhat.com> <20130509150744.GB3039@dyad.programming.kicks-ass.net> <20130509152022.GD1628@krava.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130509152022.GD1628@krava.brq.redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1622 Lines: 40 On Thu, May 09, 2013 at 05:20:22PM +0200, Jiri Olsa wrote: > On Thu, May 09, 2013 at 05:07:44PM +0200, Peter Zijlstra wrote: > > On Thu, May 09, 2013 at 03:32:15PM +0200, Jiri Olsa wrote: > > > hi, > > > adding sysfs attribute to specify the maximum allowed value > > > for perf_event_attr::precise_ip field. > > > > > > Adding functionality for simple 'p' modifier and 'precise' term > > > to get the maximum allowed value for perf_event_attr::precise_ip > > > field. > > > > > > > You've seem to lost the part explaining why we want this.. :-) > > well, initially it was an answer when we broke precise event > monitoring in kernel so I wrote automated test for it (patches 1,2,3) > https://lkml.org/lkml/2012/12/12/561 But those don't rely on the max thing right? > having maximum precise enabled with just single 'p' seemed > like good idea Doesn't seem like to me; that takes away the possibility to use less. > next step would be to enable precise automatically for 'cycles' > (when PEBS is working) asked for by Ingo > http://marc.info/?l=linux-kernel&m=135929050803963&w=2 Hurm.. I'm of two minds there. As Stephane has been pointing out for ages, cycles behaves significantly different between regular and PEBS events for some cases. Also, you really don't need the max_precise for that either. At worst you'll have a number of unsuccessful event creations. -- 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/