linux-kernel - Re: [PATCH 20/41] perf tools: Let a user specify a PMU event without any config terms

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Message-ID: <20140830085310.GA14358@krava.redhat.com>
Date:	Sat, 30 Aug 2014 10:53:10 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 20/41] perf tools: Let a user specify a PMU event without
 any config terms

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

thanks,
jirka
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