perf pmu: Add support for MetricName JSON attribute

Add support for a new JSON event attribute to name MetricExpr for better
output in perf stat.

If the event has no MetricName it uses the normal event name instead to
describe the metric.

Before

  % perf stat -a -I 1000 -e '{unc_p_clockticks,unc_p_freq_max_os_cycles}' --metric-only
           time unc_p_freq_max_os_cycles
     1.000149775     15.7
     2.000344807     19.3
     3.000502544     16.7
     4.000640656      6.6
     5.000779955      9.9

After

  % perf stat -a -I 1000 -e '{unc_p_clockticks,unc_p_freq_max_os_cycles}' --metric-only
           time freq_max_os_cycles %
     1.000149775     15.7
     2.000344807     19.3
     3.000502544     16.7
     4.000640656      6.6
     5.000779955      9.9

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20170320201711.14142-13-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index c323cce97d98..ac10cc675d39 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -803,7 +803,9 @@ void perf_stat__print_shadow_stats(struct perf_evsel *evsel,
 
                         if (expr__parse(&ratio, &pctx, &p) == 0)
                                 print_metric(ctxp, NULL, "%8.1f",
-                                        out->force_header ? evsel->name : "",
+                                        evsel->metric_name ?
+                                        evsel->metric_name :
+                                        out->force_header ?  evsel->name : "",
                                         ratio);
                         else
                                 print_metric(ctxp, NULL, NULL, "", 0);