The canonical example of this is simply a high priority loop waiting on
a Delay. Each time the Delay fires it will stir up the process list at
the priority of the suspended process (and by extension any other
priority level that might get involved) assuming of course that the
suspend is implemented to add the suspended process at the back of the
list. Not all systems actually do that - VW used to put it at the front
of thelist and so the same process would get resumed. Might still be
like that for all I know.

I think there is all the VM support you need already there, what with
the Delay etc. Note that checkForInterrupts is already involved since it
is the mechanism by which the Delay termination is noticed!

I imagine that it might be useful to add some VM support to directly
deal with a special timer for process stirring and thereby reduce by a
small amount the allocating and setting up of actual Delay objects, but
it would be a pretty minimal improvement I suspect.
tim

-- 
Tim Rowledge, tim at sumeru.stanford.edu, http://sumeru.stanford.edu/tim
Never write software that anthropomorphizes the machine.