perf report: Add --skip-empty option to suppress 0 event stat

To make the output more readable, I think it's better to remove 0's in
the output.  Also the dummy event has no event stats so it just wasts
the space.  Let's use the --skip-empty option to suppress it.

  $ perf report --stat --skip-empty

  Aggregated stats:
             TOTAL events:      16530
              MMAP events:        226
              COMM events:       1596
              EXIT events:          2
          THROTTLE events:        121
        UNTHROTTLE events:        117
              FORK events:       1595
            SAMPLE events:        719
             MMAP2 events:      12147
            CGROUP events:          2
    FINISHED_ROUND events:          2
        THREAD_MAP events:          1
           CPU_MAP events:          1
         TIME_CONV events:          1
  cycles stats:
            SAMPLE events:        719

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210427013717.1651674-5-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

5 files changed, 14 insertions, 6 deletions

diff --git a/tools/perf/util/events_stats.h b/tools/perf/util/events_stats.h
index e271c8004c89..3480bafd414b 100644
--- a/tools/perf/util/events_stats.h
+++ b/tools/perf/util/events_stats.h
@@ -50,6 +50,7 @@ struct hists_stats {
 
 void events_stats__inc(struct events_stats *stats, u32 type);
 
-size_t events_stats__fprintf(struct events_stats *stats, FILE *fp);
+size_t events_stats__fprintf(struct events_stats *stats, FILE *fp,
+			     bool skip_empty);
 
 #endif /* __PERF_EVENTS_STATS_ */
diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 691a6a777d14..65fe65ba03c2 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -2676,7 +2676,8 @@ void hist__account_cycles(struct branch_stack *bs, struct addr_location *al,
 	}
 }
 
-size_t evlist__fprintf_nr_events(struct evlist *evlist, FILE *fp)
+size_t evlist__fprintf_nr_events(struct evlist *evlist, FILE *fp,
+				 bool skip_empty)
 {
 	struct evsel *pos;
 	size_t ret = 0;
@@ -2684,6 +2685,9 @@ size_t evlist__fprintf_nr_events(struct evlist *evlist, FILE *fp)
 	evlist__for_each_entry(evlist, pos) {
 		struct hists *hists = evsel__hists(pos);
 
+		if (skip_empty && !hists->stats.nr_samples)
+			continue;
+
 		ret += fprintf(fp, "%s stats:\n", evsel__name(pos));
 		ret += fprintf(fp, "%16s events: %10d\n",
 			       "SAMPLE", hists->stats.nr_samples);
diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
index 6b0f708f08ac..5343b62476e6 100644
--- a/tools/perf/util/hist.h
+++ b/tools/perf/util/hist.h
@@ -202,7 +202,8 @@ void hists__inc_nr_samples(struct hists *hists, bool filtered);
 size_t hists__fprintf(struct hists *hists, bool show_header, int max_rows,
 		      int max_cols, float min_pcnt, FILE *fp,
 		      bool ignore_callchains);
-size_t evlist__fprintf_nr_events(struct evlist *evlist, FILE *fp);
+size_t evlist__fprintf_nr_events(struct evlist *evlist, FILE *fp,
+				 bool skip_empty);
 
 void hists__filter_by_dso(struct hists *hists);
 void hists__filter_by_thread(struct hists *hists);
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index eba3769be3f1..a6659b616e6d 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -2352,7 +2352,8 @@ size_t perf_session__fprintf_dsos_buildid(struct perf_session *session, FILE *fp
 	return machines__fprintf_dsos_buildid(&session->machines, fp, skip, parm);
 }
 
-size_t perf_session__fprintf_nr_events(struct perf_session *session, FILE *fp)
+size_t perf_session__fprintf_nr_events(struct perf_session *session, FILE *fp,
+				       bool skip_empty)
 {
 	size_t ret;
 	const char *msg = "";
@@ -2362,7 +2363,7 @@ size_t perf_session__fprintf_nr_events(struct perf_session *session, FILE *fp)
 
 	ret = fprintf(fp, "\nAggregated stats:%s\n", msg);
 
-	ret += events_stats__fprintf(&session->evlist->stats, fp);
+	ret += events_stats__fprintf(&session->evlist->stats, fp, skip_empty);
 	return ret;
 }
 
diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
index f76480166d38..e31ba4c92a6c 100644
--- a/tools/perf/util/session.h
+++ b/tools/perf/util/session.h
@@ -113,7 +113,8 @@ size_t perf_session__fprintf_dsos(struct perf_session *session, FILE *fp);
 size_t perf_session__fprintf_dsos_buildid(struct perf_session *session, FILE *fp,
 					  bool (fn)(struct dso *dso, int parm), int parm);
 
-size_t perf_session__fprintf_nr_events(struct perf_session *session, FILE *fp);
+size_t perf_session__fprintf_nr_events(struct perf_session *session, FILE *fp,
+				       bool skip_empty);
 
 struct evsel *perf_session__find_first_evtype(struct perf_session *session,
 					    unsigned int type);