Summary: Improved Conditions for Bounded Tardiness under EPDF Fair Multiprocessor
UmaMaheswari C. Devi and James H. Anderson
Department of Computer Science, The University of North Carolina, Chapel Hill, NC
The earliest-pseudo-deadline-first (EPDF) Pfair algo-
rithm is more efficient than other known Pfair scheduling
algorithms, but is not optimal on more than two processors.
In earlier work, Srinivasan and Anderson established a suffi-
cient per-task utilization restriction for ensuring a tardiness
of at most one quantum under EPDF. They also conjectured
that a tardiness bound of one quantum applies to systems
that are not restricted in any way. In this paper, we present
counterexamples that show that this conjecture is false. We
also present sufficient utilization restrictions that are more
liberal than theirs.
Pfair scheduling, originally introduced by Baruah et al.
, is the only known way of optimally scheduling re-
current real-time tasks on multiprocessors. Under Pfair