From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Ask for CLOCK_MONOTONIC which is more stable than the default perf clock.
(Ability to select a clock has been available since kernel version 4.1.)
The change should not have any significant impact on the IGT as whole
apart from maybe improving the occasional jitter in tests/tools which use
nanosleep(2) and use time slept together with perf reported time delta
either in direct or indirect calculations.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
lib/igt_perf.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/lib/igt_perf.c b/lib/igt_perf.c
index 418c1c18891c..b743859f5d29 100644
--- a/lib/igt_perf.c
+++ b/lib/igt_perf.c
@@ -1,12 +1,13 @@
-#include <stdint.h>
+#include <errno.h>
#include <fcntl.h>
-#include <unistd.h>
+#include <stdint.h>
#include <stdlib.h>
#include <string.h>
-#include <errno.h>
#include <sys/stat.h>
#include <sys/sysinfo.h>
#include <sys/sysmacros.h>
+#include <time.h>
+#include <unistd.h>
#include "igt_perf.h"
@@ -111,6 +112,8 @@ _perf_open(uint64_t type, uint64_t config, int group, uint64_t format)
attr.read_format = format;
attr.config = config;
+ attr.use_clockid = 1;
+ attr.clockid = CLOCK_MONOTONIC;
do {
ret = perf_event_open(&attr, -1, cpu++, group, 0);
--
2.25.1
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