coop/preempt [was: Re: release 0.0.0.20 and thoughts]
Tue, 22 Aug 1995 08:28:08 MET-1MEST
> On Mon, 21 Aug 1995, Rainer Blome wrote:
> > how much speedup do we get from coop? will it be so much that it is worth
> > investing the time needed to implement it?
> A _very_ good question, worthy of testing, IMO.
They way I see it it will slow down things. For example, the Amiga uses
messages to send commands to devices, let's say I make a program that
send a command to the harddrive device that says 'read 100 tracks and put it
here'. On the Amiga, the transfer from the drive to memory is probably DMA-
driven so the device suspends itself until the transfer is done. And when the
transfer is done the device code will be awaken immediately since device tasks
run at a higher priority, and the first things the device does is to reply the
As I see it this will probably max out the harddrive even with a slow processor.
Can anyone explain how coop mt can be used to elegantly do equally same
> > what is the users' model (abstract view) of a the machine? normally, you
> > don't to care about the coop/preempt issue, it's an implementation detail
> > of the os. of course, sometimes some power-user does care.
I would really hate a cooperative mt system. Different tasks have different
importance and only with pre-emptive mt it's possible to make a responsive and
> Implementing coop will be incredibly easy. Implementing proofs will be
> dramatically harder, BUT will allow many good things.
Once pre-emptive mt have been implemented the entire OS will be better, IMO.
> 1) preemptive is far harder to implement than coop.
Have you tried?
> 3) coop is easy to run under preemptive; you can just compile out the
> yields (or even just keep them in).
If you have pre-emptive, why should you want to implement coop?
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