Messages in this thread | | | Subject | Re: periods and deadlines in SCHED_DEADLINE | From | Peter Zijlstra <> | Date | Sat, 10 Jul 2010 12:36:14 +0200 |
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On Sat, 2010-07-10 at 09:11 +0200, Luca Abeni wrote: > On Fri, 2010-07-09 at 16:24 +0200, Peter Zijlstra wrote: > > On Fri, 2010-07-09 at 15:38 +0200, Raistlin wrote: > > > Basically, from the scheduling point of view, what it could happen is > > > that I'm still _NOT_ going to allow a task with runtime Q_i, deadline > > > D_i and period P_i to use more bandwidth than Q_i/P_i, I'm still using D > > > for scheduling but the passing of the simple in-kernel admission test > > > Sum_i(Q_i/P_i)<1 won't guarantee that the task will always finish its > > > jobs before D. > > > > But the tardiness would still be bounded, right? So its a valid Soft-RT > > model?
> I think that if Sum_i(Q_i/P_i)<1 but Sum_i(Q_i/min{P_i,D_i})>=1 then you > can have sporadic deadline misses, but it should still be possible to > compute an upper bound for the tardiness. > But this is just a feeling, I have no proof... :)
The paper referenced by Bjoern yesterday mentioned that Baruah et al. did that proof.
"For the considered case di < pi , Baruah et al. [7] showed that the complexity increases considerably. However, as- suming the processor utilization to be strictly less than 1, Baruah et al. [6, 7] proved that if a deadline is missed, this happens within a maximum time upper bound which can be computed."
[6] S. Baruah, A. Mok, and L. Rosier. Preemptively scheduling hard-real-time sporadic tasks on one processor. Proceedings of the 11th IEEE Real-Time Systems Symposium, December 1990.
[7] S. Baruah, L. Rosier, and R. Howell. Algorithms and complexity concerning the preemptive scheduling of peri- odic real-time tasks on one processor. Real-Time Systems, 2(4):301–324, November 1990.
It also jives well with that I remember from reading through Jim's papers on Soft-RT G-EDF. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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