WinAPI Sleep() function call sleeps for longer than expected

Question

OS: Windows 7

When calling the WinAPI Sleep() function as Sleep(1) the thread actually sleeps for 15ms. I did it 100 times in a loop and the total sleep time was 150

Answer 1

(debug or release build ?)

How are you measuring the delay ? are you using a precise method ? (queryperformancecounter)

I don't think you should rely on the Windows OS for accurate timing; it is not a real-time operating system, and there will be external "forces" that will steal time from your process.