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Schedulable Utilization Bounds for EPDF Fair Multiprocessor Scheduling ?

Summary: Schedulable Utilization Bounds for EPDF Fair
Multiprocessor Scheduling ?
UmaMaheswari C. Devi and James H. Anderson
Department of Computer Science,
The University of North Carolina, Chapel Hill, NC 27599, U.S.A.
Email: fuma,andersong@cs.unc.edu
Abstract. The earliest­pseudo­deadline­first (EPDF) algorithm is less expensive
than other known Pfair algorithms, but is not optimal for scheduling recurrent
real­time tasks on more than two processors. Prior work established sufficient
per­task weight (i.e., utilization) restrictions that ensure that tasks either do not
miss their deadlines or have bounded tardiness when scheduled under EPDF. Im­
plicit in these restrictions is the assumption that total system utilization may equal
the total available processing capacity (i.e., the total number of processors). This
paper considers an orthogonal issue --- that of determining a sufficient restriction
on the total utilization of a task set for it to be schedulable under EPDF, assuming
that there are no per­task weight restrictions. We prove that a task set with total
utilization at most 3M+1
4 is correctly scheduled under EPDF on M processors,
regardless of how large each task's weight is. At present, we do not know whether
this bound is tight. However, we provide a conterexample that shows that it cannot


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


Collections: Computer Technologies and Information Sciences