Any further comments are appreciated. On 18 March 2016 at 15:59, Darshit Shah <dar...@gmail.com> wrote:
> > > On 18 March 2016 at 14:48, Sebastian Huber < > sebastian.hu...@embedded-brains.de> wrote: > >> >> >> On 18/03/16 14:38, Darshit Shah wrote: >> >>> > "schedulable task sets would miss their deadlines since it does not >>> consider >>> > 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 >>> tasks. >>> > 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 >>> importance >>> * 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(). >> >> > That is true. Unlike the linux scheduler, all currently scheduled threads > are considered for migration, but then it seems we only decide to migrate a > thread if its priority is lower than the thread being dispatched. In case > I'm wrong then the current implementation is indeed Strong APA, just with a > bad time complexity. Else, we still have some form of a weak APA constrain > in the scheduler. > >> >> -- >> Sebastian Huber, embedded brains GmbH >> >> Address : Dornierstr. 4, D-82178 Puchheim, Germany >> Phone : +49 89 189 47 41-16 >> Fax : +49 89 189 47 41-09 >> E-Mail : sebastian.hu...@embedded-brains.de >> PGP : Public key available on request. >> >> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG. >> >> > > > -- > Thanking You, > Darshit Shah > > -- Thanking You, Darshit Shah
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