Summary: Tardiness Bounds under Global EDF Scheduling on a
Multiprocessor #
UmaMaheswari C. Devi and James H. Anderson
Department of Computer Science
The University of North Carolina at Chapel Hill
Abstract
This paper considers the scheduling of soft real­time sporadic task systems under global EDF on an iden­
tical multiprocessor. Though Pfair scheduling is theoretically optimal for hard real­time task systems on
multiprocessors, it can incur significant run­time overhead. Hence, other scheduling algorithms that are not
optimal, including EDF, have continued to receive considerable attention. However, prior research on such
algorithms has focussed mostly on hard real­time systems, where, to ensure that all deadlines are met, ap­
proximately 50% of the available processing capacity will have to be sacrificed in the worst case. This may
be overkill for soft real­time systems that can tolerate deadline misses by bounded amounts (i.e., bounded
tardiness). In this paper, we derive tardiness bounds under preemptive and non­preemptive global EDF on
multiprocessors when the total utilization of a task system is not restricted and may equal the number of pro­
cessors. Our tardiness bounds depend on per­task utilizations and execution costs --- the lower these values,
the lower the tardiness bounds. As a final remark, we note that global EDF may be superior to partitioned
EDF for multiprocessor­based soft real­time systems in that the latter does not offer any scope to improve
system utilization even if bounded tardiness can be tolerated.
# Work supported by NSF grants CCR 0204312, CNS 0309825, and CNS 0408996. The first author was also supported by an IBM

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

Collections: Computer Technologies and Information Sciences