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From: kdarling@hobbes.ncsu.edu (Kevin Darling)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: How do we change the scheduler? (Was Re: Multitasking at home...)
Message-ID: <1991Jan23.104720.24057@ncsuvx.ncsu.edu>
Date: 23 Jan 91 10:47:20 GMT
References: <MWM.91Jan7154817@raven.relay.pa.dec.com> <17210@cbmvax.commodore. <1991Jan17.204425.8037@ncsuvx.ncsu.edu> <7564@sugar.hackercorp.com>
Sender: news@ncsuvx.ncsu.edu (USENET News System)
Organization: NCSU Computing Center
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<7564@sugar.hackercorp.com> peter@sugar.hackercorp.com (Peter da Silva):
|> Whenever a task switch takes place, the kernel would first increment all
|> process Ages, and pick by the highest Age. - me
|  This would add considerably to the cost of a task switch, [...]

Not enough to worry over. I'd say that process selection and switching
really doesn't happen very often, cpu-timewise.  Hit me up with a good case.

Also, the "trick" is to increment just the queue head Age.  All others are
relative to the head's age diff.  <grin - was that murky enough? sorry>
I had a much longer explanation, but drat! when I went on vacation last
week I shut down the machine which had it on a ramdisk... if I find time
again, I'll redo it.

Also, on same subject in <1991Jan22.205630.834@zaphod.mps.ohio-state.edu>
 vidynath@function.mps.ohio-state.edu (Vidhyanath K. Rao) writes:
| The task structure size is hardcoded because of the way the AmigaDOS process
| structure is defined. Otherwise, I don't think that the task structure size
| is fixed for eternity.
| Task structure [upto v1.3 at least] has a "free" variable: [...]

I think this is one of the things I like better about say, OS9... 
the fact that system structures are not directly diddled by user processes,
and so the task structure can (and does!) grow as needed without
messing up previous work.   best - kev <kdarling@catt.ncsu.edu>