gettime: make cpuclock calibration more tolerant

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

diff --git a/gettime.c b/gettime.c
index 9988e6c54cd56a61200a17106f27a4512d9c6cb6..922768ebe5fce2d6738a27a3fe2e54533a527950 100644 (file)
--- 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