linux-kernel - [PATCH v2 2/3] perf-stat: measure t0 and ref_time after enable

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Date:   Tue, 16 Mar 2021 14:18:36 -0700
From:   Song Liu <songliubraving@...com>
To:     <linux-kernel@...r.kernel.org>
CC:     <kernel-team@...com>, <acme@...nel.org>, <acme@...hat.com>,
        <namhyung@...nel.org>, <jolsa@...nel.org>,
        Song Liu <songliubraving@...com>
Subject: [PATCH v2 2/3] 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@...com>
---
 tools/perf/builtin-stat.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 92696373da994..d030c3a49a8e4 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -931,15 +931,15 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 	/*
 	 * 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 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 		err = enable_counters();
 		if (err)
 			return -1;
+
+		t0 = rdclock();
+		clock_gettime(CLOCK_MONOTONIC, &ref_time);
+
 		status = dispatch_events(forks, timeout, interval, &times);
 	}
 
-- 
2.30.2