[okl4-developer] How to garanty CPU isolation between cells ?

[Sergio Ruocco]

Gernot Heiser wrote:
>>>>>> On Wed, 10 Dec 2008 13:51:54 +0100, Hugues Balp <hugues.balp at free.fr> said:
> HB> Robert Wetzel wrote:
> 
> Assignment of RT priorities is tricky, and your really need to
> understand what you're doing (and there isn't really much helpful
> theory). 

As even stones know by now, trying to schedule a non-trivial RT-system
with priorities is a well-proven generator of cheap academic-papers ;-)


> Which is a reason why we're trying to move away from priority-based
> scheduling (see for example the work done at NICTA and UCSC on using
> the RBED scheduler in L4).

RBED is a variation on EDF with improves on shortcomings of the vanilla
EDF, taking in account the requirements of real-world systems.

A couple of years ago I worked on a different approach to real-time
scheduling on L4, based on temporal reflection.

Although it is far from being ready-to-use, for a taste of the issues
involved in scheduling real-time stuff, you can find a paper with design
and implementation for L4, and experimental results from a non-trivial
testbed, here:

http://www.ertos.nicta.com.au/publications/papers/Ruocco_RTSS_06.abstract?bib=local

If you have any feedback, I would be happy to hear it.


> Unfortunately, most real-life RT systems are based on priorities,
> so that's likely to remain the default setup for a while...
> 
> Gernot

An unfortunate legacy brought by general-purpose priority-based
schedulers (and some academics infected by paperitis).
	
	Sergio

-- 

Dr. Sergio Ruocco   Research Fellow    http://www.disco.unimib.it/ruocco
mailto:ruocco at disco.unimib.it / sergio.ruocco at gmail.com      NOMADIS Lab
phone: +39-02-6448-7914               Mobile, embedded real-time systems
skype: 'sergioruocco'  Dip. di Informatica, Sistemistica e COmunicazione
Building U14, room 1003  Università degli Studi di Milano-Bicocca, Italy

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