From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 27 Sep 2018 23:38:21 +0000 (-0600)
Subject: gettime: slightly improve CPU clock calibration
X-Git-Tag: fio-3.11~15
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=152529ae26d1167779138b6cd30d4de10623da1b

gettime: slightly improve CPU clock calibration

We should not factor the utime_since() runtime into this, so
do the get_cpu_clock() before. In reality this probably won't
make any difference, as we're doing this tight loop for more
than a milisecond.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/gettime.c b/gettime.c
index c0f26382..7702193d 100644
--- a/gettime.c
+++ b/gettime.c
@@ -237,12 +237,11 @@ static unsigned long get_cycles_per_msec(void)
 	c_s = get_cpu_clock();
 	do {
 		__fio_gettime(&e);
+		c_e = get_cpu_clock();
 
 		elapsed = utime_since(&s, &e);
-		if (elapsed >= 1280) {
-			c_e = get_cpu_clock();
+		if (elapsed >= 1280)
 			break;
-		}
 	} while (1);
 
 	fio_clock_source = old_cs;