26/10/2023 18:28, Stephen Hemminger: > On Thu, 26 Oct 2023 16:08:02 +0200 > Morten Brørup <m...@smartsharesystems.com> wrote: > > > > > In our recent tests, nanosleep() itself took around 50 us. So you need > > > > to > > > sleep longer than that for your thread not to be runnable when the > > > nanosleep() > > > wakes up again, because 50 us has already passed in "nanosleep overhead". > > > > > > > 10 milliseconds provides plenty of margin, and corresponds to 10 > > > > jiffies on > > > a 1000 Hz kernel. (I don't know if it makes any difference for the kernel > > > scheduler if the timer crosses a jiffy border or not.) > > > > > > 10 ms looks like an eternity. > > > > Agree. It is only for functional testing, not for production! > > To be safe the sleep has to be longer than the system clock tick. > Most systems are built today with HZ=250 but really should be using HZ=1000 > on modern CPU's.
If it has to be more than 1 ms, we should mention it is a slow call which may be skipped if the thread is already blocking on something else.
