Well, that is not what I meant at all, I meant that I've seen BSD return in say 2 microseconds after calling usleep(1).

But that's usleep not sleep, which is the inaccuracy I was admitting to in the first place.

Ok, but (a) this article is talking about literally POSIX sleep(3), and (b) there is a ton of confusion on this thread about whether sleep is ms-denominated or seconds-denominated.

Sorry to pile on you, though.

Read it again. He's talking about near-zero sleep calls, not one second sleep calls.

POSIX sleep() doesn't take subsecond intervals. Maybe he's talking about usleep()?