Summary: Improved Conditions for Bounded Tardiness under EPDF Pfair
Multiprocessor Scheduling I
UmaMaheswari C. Devi a,#,1 , James H. Anderson b
a IBM India Research Laboratory,
Bangalore, KA 560071, India
b Department of Computer Science, The University of North Carolina,
Chapel Hill, NC 27599­3175 USA
Abstract
The earliest­pseudo­deadline­first (EPDF) Pfair algorithm is more e#cient than other known Pfair scheduling
algorithms, but is not optimal for scheduling recurrent real­time task systems on more than two identical pro­
cessors. Although not optimal, EPDF may be preferable for real­time systems instantiated on less­powerful
platforms, those with soft timing constraints, or those whose task composition can change at run­time. In
prior work, Srinivasan and Anderson established a su#cient per­task 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 per­task utilizations not exceed 1.0. In this paper, we present counterexamples that show that
their conjecture is false and present su#cient per­task utilization restrictions that are more liberal than
theirs. For ensuring a tardiness bound of one quantum, our restriction presents an improvement of 50% over
the previous one.

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

Collections: Computer Technologies and Information Sciences