2.6 Scheduler

[Junior <ejr@inbox.com>]

Hi All,
I post this on the arm-kernal list but perhaps I had the wrong list. 
If I also have the wrong list here, could anyone suggest a list that will be more
appropriate?

How do I determine how long a timeslice is for my scheduler once I set a RR policy?
Is their some formula  I could use (using RR policy, nice value and priority) to set a
specific (or close to it) timeslice value?
nice(), as far as I can tell, does not take a parameter, so how do I set it to a specific
value? or can I?

If instead of sleep, I use sched_yeild(), does that change any of the parameters for that
task scheduling?
If not, which is better, to sleep for a few msec or to call yield()?

Is it possible to not preemp an specific IO access? (When I want to write the serial port,
I would like to go immediately to the run state and not wait)

Is it possible to yield to a specific process/thread?

Thanks very much.
--Jr.