Why are Thread.Sleep(), time.sleep(), this_thread::sleep_for(chrono::milliseconds()), etc. inaccurate?

Question

Why are these sleep functions inaccurate?

Answer 1

Thread.Sleep(n) means block the current thread for at least the number of timeslices (or thread quantums) that can occur within n milliseconds. The length of a timeslice is different on different versions/types of Windows and different processors and generally ranges from 15 to 30 milliseconds. This means the thread is almost guaranteed to block for more than n milliseconds. The likelihood that your thread will re-awaken exactly after n milliseconds is about as impossible as impossible can be. So, Thread.Sleep is pointless for timing.
Source:
http://blogs.msmvps.com/peterritchie/2007/04/26/thread-sleep-is-a-sign-of-a-poorly-designed-program/

Answer 2

use select() syscall

Answer 3

Thank you Ali!