From: Jens Axboe <axboe@fb.com>
Date: Sat, 21 Nov 2015 00:20:06 +0000 (-0700)
Subject: gettime: make cpuclock calibration more tolerant
X-Git-Tag: fio-2.2.12~5
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=99afcdb53dc388edcc1270fe2f76d8ce1a3f9f3c;ds=sidebyside

gettime: make cpuclock calibration more tolerant

Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/gettime.c b/gettime.c
index 9988e6c5..922768eb 100644
--- a/gettime.c
+++ b/gettime.c
@@ -232,6 +232,7 @@ static unsigned long get_cycles_per_usec(void)
 	struct timeval s, e;
 	uint64_t c_s, c_e;
 	enum fio_cs old_cs = fio_clock_source;
+	uint64_t elapsed;
 
 #ifdef CONFIG_CLOCK_GETTIME
 	fio_clock_source = CS_CGETTIME;
@@ -242,8 +243,6 @@ static unsigned long get_cycles_per_usec(void)
 
 	c_s = get_cpu_clock();
 	do {
-		uint64_t elapsed;
-
 		__fio_gettime(&e);
 
 		elapsed = utime_since(&s, &e);
@@ -254,7 +253,7 @@ static unsigned long get_cycles_per_usec(void)
 	} while (1);
 
 	fio_clock_source = old_cs;
-	return (c_e - c_s + 127) >> 7;
+	return ((c_e - c_s) * 10) / elapsed;
 }
 
 #define NR_TIME_ITERS	50