This patch generally converts a division to a subtraction in fio_gettime().
Shows ~1% better iops with synthetic benchmarking at roughly the same cpu
time spent in fio_gettime().
Signed-off-by: Sam Bradshaw <sbradshaw@xxxxxxxxxx>
diff --git a/gettime.c b/gettime.c
index 248f146..e2a6241 100644
--- a/gettime.c
+++ b/gettime.c
@@ -163,17 +163,23 @@ void fio_gettime(struct timeval *tp, void fio_unused *caller)
}
#ifdef ARCH_HAVE_CPU_CLOCK
case CS_CPUCLOCK: {
- unsigned long long usecs, t;
+ unsigned long long usecs, t, delta = 0;
t = get_cpu_clock();
if (tv && t < tv->last_cycles) {
dprint(FD_TIME, "CPU clock going back in time\n");
t = tv->last_cycles;
- } else if (tv)
+ } else if (tv) {
+ if (tv->last_tv_valid)
+ delta = t - tv->last_cycles;
tv->last_cycles = t;
+ }
usecs = t / cycles_per_usec;
- tp->tv_sec = usecs / 1000000;
+ if (delta > 1000000)
+ tp->tv_sec = tv->last_tv.tv_sec;
+ else
+ tp->tv_sec = usecs / 1000000;
tp->tv_usec = usecs % 1000000;
break;
}
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