Double slack time for busy-wait

src/dedicated/i_system.c

@@ -376,6 +376,11 @@ void I_SleepDuration(precise_t duration)
 {
 #if defined(__linux__) || defined(__FreeBSD__)
 	UINT64 precision = I_GetPrecisePrecision();
+	precise_t dest = I_GetPreciseTime() + duration;
+	precise_t slack = (precision / 5000); // 0.2 ms slack
+	if (duration > slack)
+	{
+		duration -= slack;
 		struct timespec ts = {
 			.tv_sec = duration / precision,
 			.tv_nsec = duration * 1000000000 / precision % 1000000000,
@@ -383,6 +388,10 @@ void I_SleepDuration(precise_t duration)
 		int status;
 		do status = clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, &ts);
 		while (status == EINTR);
+	}
+
+	// busy-wait the rest
+	while (((INT64)dest - (INT64)I_GetPreciseTime()) > 0);
 #else
 	UINT64 precision = I_GetPrecisePrecision();
 	INT32 sleepvalue = cv_sleep.value;

src/sdl/i_system.c

@@ -2310,7 +2310,7 @@ void I_SleepDuration(precise_t duration)
 #if defined(__linux__) || defined(__FreeBSD__) || defined(__HAIKU__)
 	UINT64 precision = I_GetPrecisePrecision();
 	precise_t dest = I_GetPreciseTime() + duration;
-	precise_t slack = (precision / 10000); // 0.1 ms slack
+	precise_t slack = (precision / 5000); // 0.2 ms slack
 	if (duration > slack)
 	{
 		duration -= slack;