perf stat: Add --quiet option

Add a new --quiet option to 'perf stat'. This is useful with 'perf stat
record' to write the data only to the perf.data file, which can lower
measurement overhead because the data doesn't need to be formatted.

On my 4C desktop:

  % time ./perf stat record  -e $(python -c 'print ",".join(["cycles"]*1000)')  -a -I 1000 sleep 5
  ...
  real    0m5.377s
  user    0m0.238s
  sys     0m0.452s
  % time ./perf stat record --quiet -e $(python -c 'print ",".join(["cycles"]*1000)')  -a -I 1000 sleep 5

  real    0m5.452s
  user    0m0.183s
  sys     0m0.423s

In this example it cuts the user time by 20%. On systems with more cores
the savings are higher.

Signed-off-by: Andi Kleen <andi@firstfloor.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Link: http://lore.kernel.org/lkml/20201027002737.30942-1-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 6709578128c9..f15b2f8aa14d 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -972,6 +972,8 @@ static void print_counters(struct timespec *ts, int argc, const char **argv)
 	/* Do not print anything if we record to the pipe. */
 	if (STAT_RECORD && perf_stat.data.is_pipe)
 		return;
+	if (stat_config.quiet)
+		return;
 
 	perf_evlist__print_counters(evsel_list, &stat_config, &target,
 				    ts, argc, argv);
@@ -1171,6 +1173,8 @@ static struct option stat_options[] = {
 		    "threads of same physical core"),
 	OPT_BOOLEAN(0, "summary", &stat_config.summary,
 		       "print summary for interval mode"),
+	OPT_BOOLEAN(0, "quiet", &stat_config.quiet,
+			"don't print output (useful with record)"),
 #ifdef HAVE_LIBPFM
 	OPT_CALLBACK(0, "pfm-events", &evsel_list, "event",
 		"libpfm4 event selector. use 'perf list' to list available events",
@@ -2132,7 +2136,7 @@ int cmd_stat(int argc, const char **argv)
 		goto out;
 	}
 
-	if (!output) {
+	if (!output && !stat_config.quiet) {
 		struct timespec tm;
 		mode = append_file ? "a" : "w";