gettime: calibration rounding error

[fio.git] / gettime.c

diff --git a/gettime.c b/gettime.c
index 72fda3f8597e335be2fc4677a208f02db9fa62b7..a60b35f65f2b45df5c129a326ffc2c909afa2bdf 100644 (file)
--- a/gettime.c
+++ b/gettime.c
@@ -15,15 +15,13 @@
 #ifdef ARCH_HAVE_CPU_CLOCK
 static unsigned long cycles_per_usec;
 static unsigned long last_cycles;
+int tsc_reliable = 0;
 #endif
 static struct timeval last_tv;
 static int last_tv_valid;
 
-static struct timeval *fio_tv;
-int fio_gtod_offload = 0;
-int fio_gtod_cpu = -1;
-
-enum fio_cs fio_clock_source = CS_GTOD;
+enum fio_cs fio_clock_source = FIO_PREFERRED_CLOCK_SOURCE;
+int fio_clock_source_set = 0;
 
 #ifdef FIO_DEBUG_TIME
 
@@ -140,7 +138,11 @@ void fio_gettime(struct timeval *tp, void fio_unused *caller)
        case CS_CGETTIME: {
                struct timespec ts;
 
+#ifdef FIO_HAVE_CLOCK_MONOTONIC
+               if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0) {
+#else
                if (clock_gettime(CLOCK_REALTIME, &ts) < 0) {
+#endif
                        log_err("fio: clock_gettime fails\n");
                        assert(0);
                }
@@ -199,24 +201,26 @@ static unsigned long get_cycles_per_usec(void)
 
                gettimeofday(&e, NULL);
                elapsed = utime_since(&s, &e);
-               if (elapsed >= 10) {
+               if (elapsed >= 1280) {
                        c_e = get_cpu_clock();
                        break;
                }
        } while (1);
 
-       return c_e - c_s;
+       return (c_e - c_s + 127) >> 7;
 }
 
+#define NR_TIME_ITERS  50
+
 static void calibrate_cpu_clock(void)
 {
        double delta, mean, S;
-       unsigned long avg, cycles[10];
+       unsigned long avg, cycles[NR_TIME_ITERS];
        int i, samples;
 
        cycles[0] = get_cycles_per_usec();
        S = delta = mean = 0.0;
-       for (i = 0; i < 10; i++) {
+       for (i = 0; i < NR_TIME_ITERS; i++) {
                cycles[i] = get_cycles_per_usec();
                delta = cycles[i] - mean;
                if (delta) {
@@ -225,10 +229,10 @@ static void calibrate_cpu_clock(void)
                }
        }
 
-       S = sqrt(S / (10 - 1.0));
+       S = sqrt(S / (NR_TIME_ITERS - 1.0));
 
        samples = avg = 0;
-       for (i = 0; i < 10; i++) {
+       for (i = 0; i < NR_TIME_ITERS; i++) {
                double this = cycles[i];
 
                if ((fmax(this, mean) - fmin(this, mean)) > S)
@@ -237,10 +241,10 @@ static void calibrate_cpu_clock(void)
                avg += this;
        }
 
-       S /= 10.0;
-       mean /= 10.0;
+       S /= (double) NR_TIME_ITERS;
+       mean /= (double) NR_TIME_ITERS;
 
-       for (i = 0; i < 10; i++)
+       for (i = 0; i < NR_TIME_ITERS; i++)
                dprint(FD_TIME, "cycles[%d]=%lu\n", i, cycles[i] / 10);
 
        avg /= (samples * 10);
@@ -248,7 +252,6 @@ static void calibrate_cpu_clock(void)
        dprint(FD_TIME, "mean=%f, S=%f\n", mean, S);
 
        cycles_per_usec = avg;
-
 }
 #else
 static void calibrate_cpu_clock(void)
@@ -260,15 +263,81 @@ void fio_clock_init(void)
 {
        last_tv_valid = 0;
        calibrate_cpu_clock();
+
+       /*
+        * If the arch sets tsc_reliable != 0, then it must be good enough
+        * to use as THE clock source. For x86 CPUs, this means the TSC
+        * runs at a constant rate and is synced across CPU cores.
+        */
+       if (tsc_reliable) {
+               if (!fio_clock_source_set)
+                       fio_clock_source = CS_CPUCLOCK;
+       } else if (fio_clock_source == CS_CPUCLOCK)
+               log_info("fio: clocksource=cpu may not be reliable\n");
+}
+
+unsigned long long utime_since(struct timeval *s, struct timeval *e)
+{
+       long sec, usec;
+       unsigned long long ret;
+
+       sec = e->tv_sec - s->tv_sec;
+       usec = e->tv_usec - s->tv_usec;
+       if (sec > 0 && usec < 0) {
+               sec--;
+               usec += 1000000;
+       }
+
+       /*
+        * time warp bug on some kernels?
+        */
+       if (sec < 0 || (sec == 0 && usec < 0))
+               return 0;
+
+       ret = sec * 1000000ULL + usec;
+
+       return ret;
+}
+
+unsigned long long utime_since_now(struct timeval *s)
+{
+       struct timeval t;
+
+       fio_gettime(&t, NULL);
+       return utime_since(s, &t);
 }
 
-void fio_gtod_init(void)
+unsigned long mtime_since(struct timeval *s, struct timeval *e)
 {
-       fio_tv = smalloc(sizeof(struct timeval));
-       assert(fio_tv);
+       long sec, usec, ret;
+
+       sec = e->tv_sec - s->tv_sec;
+       usec = e->tv_usec - s->tv_usec;
+       if (sec > 0 && usec < 0) {
+               sec--;
+               usec += 1000000;
+       }
+
+       if (sec < 0 || (sec == 0 && usec < 0))
+               return 0;
+
+       sec *= 1000UL;
+       usec /= 1000UL;
+       ret = sec + usec;
+
+       return ret;
+}
+
+unsigned long mtime_since_now(struct timeval *s)
+{
+       struct timeval t;
+       void *p = __builtin_return_address(0);
+
+       fio_gettime(&t, p);
+       return mtime_since(s, &t);
 }
 
-void fio_gtod_update(void)
+unsigned long time_since_now(struct timeval *s)
 {
-       gettimeofday(fio_tv, NULL);
+       return mtime_since_now(s) / 1000;
 }