EDF Pluggable Scheduler

Gedare Bloom gedare at gwu.edu
Thu Mar 31 19:15:28 UTC 2011

Hi Petr,

This is an interesting project. I did not concern myself with
synchronization issues, so I did not implement anything to deal with
deadilne interchange. With the pluggable scheduler framework, it
should be sufficient to implement Scheduler_Update -- I don't know if
enough information is passed currently, you may need to ensure that
current_priority always represents the thread's deadline.

I consider this a failing of the tight integration of threads and
priority values. I tried to refactor this priority handling into a
separate Priority Handler, but it was hard to separate the priority
logic and still have efficient thread management.  It might be
worthwhile to reconsider this in light of the need to handle priority
in an opaque way in the mutex code.

There was another edf implementation done (
http://code.google.com/p/rtems-edf/ ) that is based on Martin's work
as well. It was implemented before the pluggable interface.

I have not revised my EDF to fit the current pluggable framework (it
is close, but some variations), as I am waiting on the merge of the
red-black tree (https://www.rtems.org/bugzilla/show_bug.cgi?id=1641).

Good luck, and feel free to contact me for more details/assistance.

On Thu, Mar 31, 2011 at 6:59 AM, Petr Benes <benesp16 at fel.cvut.cz> wrote:
> Dear Mr. Bloom,
> I am applying to you for an advice regarding RTEMS scheduling.
> I am currently working on my master thesis at CTU Prague dealing with
> porting a resource reservation framework (www.frescor.org) onto RTEMS. I
> need to ensure a temporal independence/isolation of separate tasks and for
> this we are to use an EDF scheduler with an incorporated CBS (Constant
> Bandwidth Server).
> As far as I am concerned, you work on some EDF or you have it done. I assume
> it is a pluggable one, since there is the feature in RTEMS 4.11 already
> implemented.
> I have just finished a quickie implementation of a pluggable EDF on my own
> (git at rtime.felk.cvut.cz:/rtems-pluggable-edf) having Martin Molnar's one as
> an example. I guess you know each other (he is also from CTU).
> The question I have is whether you happen to have some solution or at least
> an idea how to handle Deadline interchange and you are willing to share the
> experience. There is nothing reasonable proposed in the thesis by Martin
> Molnar (https://dip.felk.cvut.cz/browse/pdfcache/molnam1_2006dipl.pdf). So
> far, for sake of simplicity, I was thinking about some kind of hack making
> use of the current RAPs used by priority scheduling.
> Best regards
> Bc. Petr Beneš
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