+ break;
+ }
+#ifdef ARCH_HAVE_CPU_CLOCK
+ case CS_CPUCLOCK: {
+ unsigned long long usecs, t;
+
+ t = get_cpu_clock();
+ if (t < last_cycles) {
+ dprint(FD_TIME, "CPU clock going back in time\n");
+ t = last_cycles;
+ }
+
+ usecs = t / cycles_per_usec;
+ tp->tv_sec = usecs / 1000000;
+ tp->tv_usec = usecs % 1000000;
+ last_cycles = t;
+ break;
+ }
+#endif
+ default:
+ log_err("fio: invalid clock source %d\n", fio_clock_source);
+ break;
+ }
+
+ /*
+ * If Linux is using the tsc clock on non-synced processors,
+ * sometimes time can appear to drift backwards. Fix that up.
+ */
+ if (last_tv_valid) {
+ if (tp->tv_sec < last_tv.tv_sec)
+ tp->tv_sec = last_tv.tv_sec;
+ else if (last_tv.tv_sec == tp->tv_sec &&
+ tp->tv_usec < last_tv.tv_usec)
+ tp->tv_usec = last_tv.tv_usec;
+ }
+ last_tv_valid = 1;
+ memcpy(&last_tv, tp, sizeof(*tp));
+}
+
+#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);
+ }