Participation in GSoC 2016
sebastian.huber at embedded-brains.de
Fri Mar 18 13:48:48 UTC 2016
On 18/03/16 14:38, Darshit Shah wrote:
> > "schedulable task sets would miss their deadlines since it does not
> > migrating high priority tasks"
> > I think this is not correct. The current APA scheduler should implement
> > strong APA. However, it may iterate several times over all (!) ready
> > This is the actual problem.
> I may be wrong, but I think the current implementation does indeed not
> consider strong APA guarantees.
> The `_Scheduler_priority_affinity_SMP_Get_lowest_scheduled` method
> tries to find a thread that needs to be migrated to another core in
> order to schedule the selected thread. In this method, on line 274 is
> the comment:
> * If we didn't find a thread which is of equal or lower
> * than filter thread is, then we can't schedule the filter thread
> * to execute.
> If I understand this comment correctly, the scheduler does not
> consider threads for migration if they are not of "equal or lower
> importance" than the filter thread.
In contrast to the Linux push/pull scheduler you search here in the set
of all scheduled/ready threads and not just in your local queue. I
didn't look into the details, but I think this is enough for strong APA.
See also _Scheduler_priority_affinity_SMP_Check_for_migrations().
Sebastian Huber, embedded brains GmbH
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E-Mail : sebastian.huber at embedded-brains.de
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