linux-kernel - Re: [PATCH 1/3] perf: record TRACE_INFO only if using tracepoints and SAMPLE

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Date:	Tue, 4 May 2010 18:18:43 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Tom Zanussi <tzanussi@...il.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 1/3] perf: record TRACE_INFO only if using tracepoints
 and SAMPLE_RAW

Em Tue, May 04, 2010 at 07:06:45PM +0200, Frederic Weisbecker escreveu:
> On Tue, May 04, 2010 at 11:00:05AM -0300, Arnaldo Carvalho de Melo wrote:
> > From: Tom Zanussi <tzanussi@...il.com>
> > 
> > The current perf code implicitly assumes SAMPLE_RAW means tracepoints
> > are being used, but doesn't check for that.  It happily records the
> > TRACE_INFO even if SAMPLE_RAW is used without tracepoints, but when the
> > perf data is read it won't go any further when it finds TRACE_INFO but
> > no tracepoints, and displays misleading errors.
> > 
> > This adds a check for both in perf-record, and won't record TRACE_INFO
> > unless both are true.  This at least allows perf report -D to dump raw
> > events, and avoids triggering a misleading error condition in perf
> > trace.  It doesn't actually enable the non-tracepoint raw events to be
> > displayed in perf trace, since perf trace currently only deals with
> > tracepoint events.
> > 
> > Cc: Frédéric Weisbecker <fweisbec@...il.com>
> > Cc: Mike Galbraith <efault@....de>
> > Cc: Paul Mackerras <paulus@...ba.org>
> > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > LKML-Reference: <1272865861.7932.16.camel@...picana>
> > Signed-off-by: Tom Zanussi <tzanussi@...il.com>
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> > ---
> >  tools/perf/builtin-record.c        |   35 +++++++++++++++++++++--------------
> >  tools/perf/util/header.c           |    1 -
> >  tools/perf/util/parse-events.h     |    1 +
> >  tools/perf/util/trace-event-info.c |    5 +++++
> >  4 files changed, 27 insertions(+), 15 deletions(-)
> > 
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index ac989e9..0ff67d1 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -560,11 +560,12 @@ static int __cmd_record(int argc, const char **argv)
> >  			return err;
> >  	}
> >  
> > -	if (raw_samples) {
> > +	if (raw_samples && have_tracepoints(attrs, nr_counters)) {
> >  		perf_header__set_feat(&session->header, HEADER_TRACE_INFO);
> >  	} else {
> 
> 
> 
> Using get_tracepoints_path() is a bit costly just to check if we use
> tracepoints as it allocates and fill the paths.

Can you please send a fix?

- Arnaldo
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