Re: [PATCH 1/3] perf: record TRACE_INFO only if using tracepoints and SAMPLE_RAW

[Frederic Weisbecker <fweisbec@gmail.com>]

On Tue, May 04, 2010 at 11:00:05AM -0300, Arnaldo Carvalho de Melo wrote:
> From: Tom Zanussi <tzanussi@gmail.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@gmail.com>
> Cc: Mike Galbraith <efault@gmx.de>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> LKML-Reference: <1272865861.7932.16.camel@tropicana>
> Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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.



>  		for (i = 0; i < nr_counters; i++) {
> -			if (attrs[i].sample_type & PERF_SAMPLE_RAW) {
> +			if (attrs[i].sample_type & PERF_SAMPLE_RAW &&
> +				attrs[i].type == PERF_TYPE_TRACEPOINT) {
>  				perf_header__set_feat(&session->header, HEADER_TRACE_INFO);
>  				break;
>  			}



In fact now we always have PERF_SAMPLE_RAW for tracepoints.



> @@ -662,19 +663,25 @@ static int __cmd_record(int argc, const char **argv)
>  			return err;
>  		}
>  
> -		err = event__synthesize_tracing_data(output, attrs,
> -						     nr_counters,
> -						     process_synthesized_event,
> -						     session);
> -		/*
> -		 * FIXME err <= 0 here actually means that there were no tracepoints
> -		 * so its not really an error, just that we don't need to synthesize
> -		 * anything.
> -		 * We really have to return this more properly and also propagate
> -		 * errors that now are calling die()
> -		 */
> -		if (err > 0)
> +		if (have_tracepoints(attrs, nr_counters)) {
> +			/*
> +			 * FIXME err <= 0 here actually means that
> +			 * there were no tracepoints so its not really
> +			 * an error, just that we don't need to
> +			 * synthesize anything.  We really have to
> +			 * return this more properly and also
> +			 * propagate errors that now are calling die()
> +			 */
> +			err = event__synthesize_tracing_data(output, attrs,
> +							     nr_counters,
> +							     process_synthesized_event,
> +							     session);
> +			if (err <= 0) {
> +				pr_err("Couldn't record tracing data.\n");
> +				return err;
> +			}
>  			advance_output(err);
> +		}
>  	}



Now get_tracepoints_path() may be called three times. You are leaking some
memory by doing that as the paths are reallocated without beeing released.




>  
>  	machine = perf_session__find_host_machine(session);
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 79da0e5..2b9f898 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -436,7 +436,6 @@ static int perf_header__adds_write(struct perf_header *self, int fd)
>  		trace_sec->size = lseek(fd, 0, SEEK_CUR) - trace_sec->offset;
>  	}
>  
> -
>  	if (perf_header__has_feat(self, HEADER_BUILD_ID)) {
>  		struct perf_file_section *buildid_sec;
>  
> diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
> index b8c1f64..fc4ab3f 100644
> --- a/tools/perf/util/parse-events.h
> +++ b/tools/perf/util/parse-events.h
> @@ -13,6 +13,7 @@ struct tracepoint_path {
>  };
>  
>  extern struct tracepoint_path *tracepoint_id_to_path(u64 config);
> +extern bool have_tracepoints(struct perf_event_attr *pattrs, int nb_events);
>  
>  extern int			nr_counters;
>  
> diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
> index 30cd9b5..0a1fb9d 100644
> --- a/tools/perf/util/trace-event-info.c
> +++ b/tools/perf/util/trace-event-info.c
> @@ -487,6 +487,11 @@ get_tracepoints_path(struct perf_event_attr *pattrs, int nb_events)
>  	return nr_tracepoints > 0 ? path.next : NULL;
>  }
>  
> +bool have_tracepoints(struct perf_event_attr *pattrs, int nb_events)
> +{
> +	return get_tracepoints_path(pattrs, nb_events) ? true : false;
> +}
> +
>  int read_tracing_data(int fd, struct perf_event_attr *pattrs, int nb_events)
>  {
>  	char buf[BUFSIZ];
> -- 
> 1.6.2.5
>