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Improved Conditions for Bounded Tardiness under EPDF Pfair Multiprocessor Scheduling$

Summary: Improved Conditions for Bounded Tardiness under EPDF Pfair
Multiprocessor Scheduling$
UmaMaheswari C. Devia,,1
, James H. Andersonb
aIBM India Research Laboratory,
Bangalore, KA 560071, India
bDepartment of Computer Science, The University of North Carolina,
Chapel Hill, NC 27599-3175 USA
The earliest-pseudo-deadline-first (EPDF) Pfair algorithm is more efficient than other known Pfair scheduling
algorithms, but is not optimal for scheduling recurrent real-time task systems on more than two identical pro-
cessors. Although not optimal, EPDF may be preferable for real-time systems instantiated on less-powerful
platforms, those with soft timing constraints, or those whose task composition can change at run-time. In
prior work, Srinivasan and Anderson established a sufficient per-task utilization restriction for ensuring a
tardiness of at most q quanta, where q 1, under EPDF. They also conjectured that under this algorithm,
a tardiness bound of one quantum applies to task systems that are not subject to any restriction other
than the obvious restrictions, namely, that the total system utilization not exceed the available processing
capacity and per-task utilizations not exceed 1.0. In this paper, we present counterexamples that show that
their conjecture is false and present sufficient per-task utilization restrictions that are more liberal than
theirs. For ensuring a tardiness bound of one quantum, our restriction presents an improvement of 50% over


Source: Anderson, James - Department of Computer Science, University of North Carolina at Chapel Hill


Collections: Computer Technologies and Information Sciences