Use absolute time to wake up the real time thread at a regular interval

clock-res/src/clockres.c

@@ -46,7 +46,7 @@ static inline uint64_t min(uint64_t a, uint64_t b);
 
 // Real-time thread
 static void *timerthread(void *p) {
-  struct timespec previous, current;
+  struct timespec previous, current, next;
   struct sched_param priority;
   cpu_set_t mask;
   uint64_t diff;
@@ -74,6 +74,8 @@ static void *timerthread(void *p) {
   // Start tracing
   if (param->enable_tracing) tracing(1);
 
+  clock_gettime(CLOCK_ID, &next);
+
   // Measurement loop
   for (stat->nb_cycles = 0;; stat->nb_cycles++) {
     if (param->max_cycles && (stat->nb_cycles >= param->max_cycles)) break;
@@ -101,7 +103,14 @@ static void *timerthread(void *p) {
     stat->max_res = max(stat->max_res, diff);
     stat->min_res = min(stat->min_res, diff);
 
-    usleep(param->interval);
+    next.tv_nsec += 10000000;
+
+    if(next.tv_nsec >= NSEC_PER_SEC) {
+      next.tv_sec += 1;
+      next.tv_nsec -= NSEC_PER_SEC;
+    }
+
+    clock_nanosleep(CLOCK_ID, TIMER_ABSTIME, &next, NULL);
   }
 
   if (param->enable_tracing) tracing(0);