+#ifdef ARCH_HAVE_CPU_CLOCK
+static unsigned long get_cycles_per_usec(void)
+{
+ struct timeval s, e;
+ unsigned long long c_s, c_e;
+
+ gettimeofday(&s, NULL);
+ c_s = get_cpu_clock();
+ do {
+ unsigned long long elapsed;
+
+ gettimeofday(&e, NULL);
+ elapsed = utime_since(&s, &e);
+ if (elapsed >= 10) {
+ c_e = get_cpu_clock();
+ break;
+ }
+ } while (1);
+
+ return c_e - c_s;
+}
+
+static void calibrate_cpu_clock(void)
+{
+ double delta, mean, S;
+ unsigned long avg, cycles[10];
+ int i, samples;
+
+ cycles[0] = get_cycles_per_usec();
+ S = delta = mean = 0.0;
+ for (i = 0; i < 10; i++) {
+ cycles[i] = get_cycles_per_usec();
+ delta = cycles[i] - mean;
+ if (delta) {
+ mean += delta / (i + 1.0);
+ S += delta * (cycles[i] - mean);
+ }
+ }
+
+ S = sqrt(S / (10 - 1.0));
+
+ samples = avg = 0;
+ for (i = 0; i < 10; i++) {
+ double this = cycles[i];
+
+ if ((fmax(this, mean) - fmin(this, mean)) > S)
+ continue;
+ samples++;
+ avg += this;
+ }
+
+ S /= 10.0;
+ mean /= 10.0;
+
+ for (i = 0; i < 10; i++)
+ dprint(FD_TIME, "cycles[%d]=%lu\n", i, cycles[i] / 10);
+
+ avg /= (samples * 10);
+ dprint(FD_TIME, "avg: %lu\n", avg);
+ dprint(FD_TIME, "mean=%f, S=%f\n", mean, S);
+
+ cycles_per_usec = avg;
+
+}
+#else
+static void calibrate_cpu_clock(void)
+{
+}
+#endif
+
+void fio_clock_init(void)
+{
+ last_tv_valid = 0;
+ calibrate_cpu_clock();
+}
+