From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752660AbaIATL7 (ORCPT ); Mon, 1 Sep 2014 15:11:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37853 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752139AbaIATL6 (ORCPT ); Mon, 1 Sep 2014 15:11:58 -0400 Date: Mon, 1 Sep 2014 21:11:07 +0200 From: Jiri Olsa To: Adrian Hunter Cc: Arnaldo Carvalho de Melo , Peter Zijlstra , linux-kernel@vger.kernel.org, David Ahern , Frederic Weisbecker , Namhyung Kim , Paul Mackerras , Stephane Eranian Subject: Re: [PATCH 20/41] perf tools: Let a user specify a PMU event without any config terms Message-ID: <20140901191107.GE1900@krava.redhat.com> References: <1405332185-4050-1-git-send-email-adrian.hunter@intel.com> <1405332185-4050-21-git-send-email-adrian.hunter@intel.com> <20140716142510.GE9441@krava.redhat.com> <53C6948C.2080103@intel.com> <20140716182214.GB32716@krava.redhat.com> <5400CB13.4040004@intel.com> <20140830085310.GA14358@krava.redhat.com> <540411C5.8030207@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <540411C5.8030207@intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 01, 2014 at 09:27:17AM +0300, Adrian Hunter wrote: > On 08/30/2014 11:53 AM, Jiri Olsa wrote: > > On Fri, Aug 29, 2014 at 09:48:51PM +0300, Adrian Hunter wrote: > >> On 16/07/2014 9:22 p.m., Jiri Olsa wrote: > >>> On Wed, Jul 16, 2014 at 06:04:44PM +0300, Adrian Hunter wrote: > >>>> On 16/07/2014 5:25 p.m., Jiri Olsa wrote: > >>>>> On Mon, Jul 14, 2014 at 01:02:44PM +0300, Adrian Hunter wrote: > >>>>>> This enables a PMU event to be specified in the form: > >>>>>> > >>>>>> pmu// > >>>>>> > >>>>>> which is effectively the same as: > >>>>>> > >>>>>> pmu/config=0/ > >>>>>> > >>>>>> This patch is a precursor to defining > >>>>>> default config for a PMU. > >>>>> > >>>>> I understand the need for default config, but could you please elaborate > >>>>> why do we want to parse 'pmu//' as an event string string? > >>>> > >>>> Currently the parser requires the slashes to identify a PMU event > >>>> as opposed to a hardware or other kind of event. > >>> > >>> right, so why do we want to parse 'pmu//' as an event string? ;-) > >> > >> I am not sure what you mean. Here I am using 'pmu' as a placeholder > >> for a real PMU name. So actual event strings are 'intel_bts//' or > >> 'intel_pt//' or 'intel_pt/tsc=0,noretcomp=1/' > > > > so the consequence of default arguments is that you can > > specify event just by the pmu name, like: > > -e intel_pt// > > > > which means (with default attributes): > > -e intel_pt/tsc=1,noretcomp=0/ > > > > I guess I wanted to hear more elaboration why is this better > > than the current way we have by defining an alias, like: > > > > krava alias: "tsc=1,noretcomp=0" > > > > -e intel_pt/krava/ > > > > which gives the same result > > The default value must be provided by perf tools not the kernel e.g. > an older version of perf tools will not be aware of new hardware > features that the kernel may know about. If the kernel enables > new features by default then the tool may fail. Thus the default > value has to be under the control of the tools not the kernel, so > a sysfs alias will not work. > I dont follow, could u provide some example? why the tool needs to understand.. it will just take the alias and apply/use it? The alias follows the format logic, which tells how to apply values on perf_event_attr.. and the kernel knows best what's supported in its version.. jirka