Re: Bad sleep time resolution of nanosleep(2)

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Tue, Nov 24, 2015 at 12:25:45AM +0100, Rhialto wrote:
> In the context of the machine simulator simh, which needs some accurate
> timing now and then, I have come across an example of rather bad time
> resolution of the nanosleep() system call.  The minimal sleep time seems
> to be 20 ms, even if you ask for just 1 ms delay. If you ask for longer
> sleeps, the discrepancy becomes relatively less but remains substantial:
> 20 ms becomes 30 ms, and 40 ms becomes 50.

Well, it is rounded up first to whole ticks, that's the easy part. Next
the callout is scheduled at the tick boundary and then the LWP is
unblocked and scheduled again. It will run in the next scheduling cycle
unless nothing else is running?

Joerg