perf stat: Show average value on multiple runs

When -r option is used, perf stat runs the command multiple times and
update stats in the evsel->stats.res_stats for global aggregation.  But
the value is never used and the value it prints at the end is just the
value from the last run.  I think we should print the average number of
multiple runs.

Add evlist__copy_res_stats() to update the aggr counter (for display)
using the values in the evsel->stats.res_stats.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230616073211.1057936-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

@@ -2831,8 +2831,11 @@ int cmd_stat(int argc, const char **argv)
 		}
 	}
 
-	if (!forever && status != -1 && (!interval || stat_config.summary))
+	if (!forever && status != -1 && (!interval || stat_config.summary)) {
+		if (stat_config.run_count > 1)
+			evlist__copy_res_stats(&stat_config, evsel_list);
 		print_counters(NULL, argc, argv);
+	}
 
 	evlist__finalize_ctlfd(evsel_list);
 

tools/perf/util/stat.c

@@ -264,6 +264,28 @@ void evlist__copy_prev_raw_counts(struct evlist *evlist)
 		evsel__copy_prev_raw_counts(evsel);
 }
 
+static void evsel__copy_res_stats(struct evsel *evsel)
+{
+	struct perf_stat_evsel *ps = evsel->stats;
+
+	/*
+	 * For GLOBAL aggregation mode, it updates the counts for each run
+	 * in the evsel->stats.res_stats.  See perf_stat_process_counter().
+	 */
+	*ps->aggr[0].counts.values = avg_stats(&ps->res_stats);
+}
+
+void evlist__copy_res_stats(struct perf_stat_config *config, struct evlist *evlist)
+{
+	struct evsel *evsel;
+
+	if (config->aggr_mode != AGGR_GLOBAL)
+		return;
+
+	evlist__for_each_entry(evlist, evsel)
+		evsel__copy_res_stats(evsel);
+}
+
 static size_t pkg_id_hash(long __key, void *ctx __maybe_unused)
 {
 	uint64_t *key = (uint64_t *) __key;

tools/perf/util/stat.h

@@ -197,6 +197,7 @@ void evlist__save_aggr_prev_raw_counts(struct evlist *evlist);
 
 int evlist__alloc_aggr_stats(struct evlist *evlist, int nr_aggr);
 void evlist__reset_aggr_stats(struct evlist *evlist);
+void evlist__copy_res_stats(struct perf_stat_config *config, struct evlist *evlist);
 
 int perf_stat_process_counter(struct perf_stat_config *config,
 			      struct evsel *counter);