From: Song Liu <songliubraving@fb.com>
Date: Tue, 16 Mar 2021 21:18:36 +0000 (-0700)
Subject: perf stat: Measure 't0' and 'ref_time' after enable_counters()
X-Git-Tag: v5.13-rc1~73^2~93
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=435b46ef1d9fd904089199da16a21ade0701537f;p=thirdparty%2Fkernel%2Flinux.git

perf stat: Measure 't0' and 'ref_time' after enable_counters()

Take measurements of 't0' and 'ref_time' after enable_counters(), so
that they only measure the time consumed when the counters are enabled.

Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Andi Kleen <andi@firstfloor.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: kernel-team@fb.com
Link: http://lore.kernel.org/lkml/20210316211837.910506-3-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index d34e22dce2c82..4bb48c6b66980 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -931,15 +931,15 @@ try_again_reset:
 	/*
 	 * Enable counters and exec the command:
 	 */
-	t0 = rdclock();
-	clock_gettime(CLOCK_MONOTONIC, &ref_time);
-
 	if (forks) {
 		evlist__start_workload(evsel_list);
 		err = enable_counters();
 		if (err)
 			return -1;
 
+		t0 = rdclock();
+		clock_gettime(CLOCK_MONOTONIC, &ref_time);
+
 		if (interval || timeout || evlist__ctlfd_initialized(evsel_list))
 			status = dispatch_events(forks, timeout, interval, &times);
 		if (child_pid != -1) {
@@ -960,6 +960,10 @@ try_again_reset:
 		err = enable_counters();
 		if (err)
 			return -1;
+
+		t0 = rdclock();
+		clock_gettime(CLOCK_MONOTONIC, &ref_time);
+
 		status = dispatch_events(forks, timeout, interval, &times);
 	}