Preemptive Multitasking

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2 total messages Started by Frank Hrebabetzky - CERTI - CCE ... Wed, 27 Mar 1996 17:21

#1217

Author: Frank Hrebabetzky - CERTI - CCE ...
Date: Wed, 27 Mar 1996 17:21

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There have been some votings for/against preemptive multitasking lately.

Without any doubt, nobody would like to modify a tested numerical 
algorithm in order to realize it as background task in a cooperative 
multitasking environment. In this case preemptive multitasking can ease 
life a lot.

Cooperative multitasking on the other hand does not carry the task 
switching overhead with it. So each little independent task can 
be realized as background task and there can be a lot of them active 
at the same time without slowing down the system.

I hope I am not annoying anybod with my standard example of a closed control
loop, but for this project the Oberon (cooperative) multitasking helped me a 
lot. The control loop is a background task, performing one control step 
each main loop cycle. Real-time graphical visualization as y-t-graphics 
is another background task with an update rate of about 5 point/s. 
Survey of some limits generating alerts is realized as another background 
task. Periodical switching of the required parameters for measurement of 
system speed: just another background task. Change of control parameters 
during stabilization: background task.

If your need is true real-time control however, you need preemptive 
multitasking. In Oberon for PC (the only version where I have some 
experience) this can be realized to some degree with interrupts.

-----------------------------------------------------------
Fundacao CERTI			Tel.:	+55 / 48 / 234-3000
Dr. Frank Hrebabetzky		Fax:	+55 / 48 / 234-1514
Campus da UFSC, CP 5053		email:	fh@mbox1.ufsc.br
Florianopolis, SC		        fh@certi.ufsc.br
88040-970
Brasil

Re: Preemptive Multitasking

#1240

Author: R Louis Besse
Date: Sat, 30 Mar 1996 23:33

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Would it be too far down the food chain for this group, that 
I should ask for explanations between "cooperative" and 
"preemptive" multitasking?

If so, can someone point me to an online resource for 
understanding them?

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