Dik. Trochu googlovani k te funkci. Nasel jsem i pekne videjko a trocha to prepsal (protoze mi to neslo uplne vlozit, ale s tim se jeste poperu). A meri to.
LARGE_INTEGER clock_frequency;
LARGE_INTEGER start_time;
LARGE_INTEGER end_time;
LARGE_INTEGER delta;
float delta_second;
QueryPerformanceFrequency(&clock_frequency);
QueryPerformanceCounter(&start_time);
Sleep(200);
QueryPerformanceCounter(&end_time);
delta.QuadPart = end_time.QuadPart - start_time.QuadPart;
delta_second = ((float)delta.QuadPart) / clock_frequency.QuadPart;
ui->textEdit->append(QString::number(delta_second));