Re: [ProgSoc] XINU emulator

[Greg Kopff <gkopff@nospam.powersource.com.au>]

On Tue, 12 Jun 2001 16:37, you wrote:
> There are still a lot of features
> not included (for example, nmos does not have priorities at all,
> it just schedules round in a ring). Since you were rewriting the
> priority system anyhow it probably wouldn't be much harder to
> actually write a priority system from scratch.

Yeah, my modified scheduler is a bit of a hack anyway.  I didn't touch 
Comer's priority queues - if I had it would have been nicer.  To make it 
"traditional unix like" (as described in Stalling's Operating Systems 4th Ed) 
- meaning cpu bound processes are penalised and have their effective priority 
lowered - I have to recalculate the priority of all ready processes every 
time resched() is called.

And by using his priority queues, I have to pop the the tail, adjust the 
priority, put it aside, pop the new tail ... repeat for all ready processes 
-- then I stuff them all back in and the queue is automajically ordered 
internally, leaving the highest priority one at the tail, ready to pop and 
ctxsw.

It works though, and I found & fixed my tutors bugs too, so I deserve marks 
for that... ;-)

-- 
 Greg Kopff
===================================================
gkopff@nospam.powersource.com.au      PowerSource Software
Technical Director    http://www.powersource.com.au
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Gentlemen! You can't fight in here, this is the
  War Room! - President Merkin Muffley
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