perf stat: Add 'walltime_nsecs_stats' pointer to 'struct perf_stat_config'

Add 'walltime_nsecs_stats' pointer to 'struct perf_stat_config', so that
it can be passed around and used outside the 'perf stat' command.

It's initialized to point to stat's walltime_nsecs_stats value.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180830063252.23729-32-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

@@ -200,6 +200,7 @@ static struct perf_stat_config stat_config = {
 	.unit_width		= 4, /* strlen("unit") */
 	.run_count		= 1,
 	.metric_only_len	= METRIC_ONLY_LEN,
+	.walltime_nsecs_stats	= &walltime_nsecs_stats,
 };
 
 static bool is_duration_time(struct perf_evsel *evsel)
@@ -1671,7 +1672,7 @@ static double timeval2double(struct timeval *t)
 
 static void print_footer(struct perf_stat_config *config)
 {
-	double avg = avg_stats(&walltime_nsecs_stats) / NSEC_PER_SEC;
+	double avg = avg_stats(config->walltime_nsecs_stats) / NSEC_PER_SEC;
 	FILE *output = config->output;
 	int n;
 
@@ -1690,7 +1691,7 @@ static void print_footer(struct perf_stat_config *config)
 			fprintf(output, " %17.9f seconds sys\n", ru_stime);
 		}
 	} else {
-		double sd = stddev_stats(&walltime_nsecs_stats) / NSEC_PER_SEC;
+		double sd = stddev_stats(config->walltime_nsecs_stats) / NSEC_PER_SEC;
 		/*
 		 * Display at most 2 more significant
 		 * digits than the stddev inaccuracy.

tools/perf/util/stat.h

@@ -105,6 +105,7 @@ struct perf_stat_config {
 	struct runtime_stat	*stats;
 	int			 stats_num;
 	const char		*csv_sep;
+	struct stats		*walltime_nsecs_stats;
 };
 
 void update_stats(struct stats *stats, u64 val);