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Mixed Pfair/ERfair Scheduling of Asynchronous Periodic Tasks

Summary: Mixed Pfair/ERfair Scheduling of Asynchronous
Periodic Tasks 
James H. Anderson and Anand Srinivasan
Department of Computer Science, University of North Carolina
Chapel Hill, NC 27599-3175
E-mail: fanderson,anandsg@cs.unc.edu
Phone: (919) 962-1757
December 2000
There has been much recent interest in multiprocessor Pfair and ERfair scheduling algorithms. Under
Pfair scheduling, each task is broken into quantum-length subtasks, each of which must execute within a
\window" of time slots. These windows divide each period of a task into potentially overlapping subintervals
of approximately equal length. \Early-release" fair (ERfair) scheduling was recently proposed as a work-
conserving variant of Pfair scheduling. Under ERfair scheduling, subtasks within the same job are allowed
to execute before their Pfair windows.
In this paper, we prove that a simpli ed variant of the PD Pfair algorithm, called PD 2 , is optimal for
scheduling any mix of early-release and non-early-release asynchronous tasks on a multiprocessor. This
result breaks new ground in two ways. First, we are the rst to consider the problem of scheduling both
early-release and non-early-release tasks under a common framework. Second, all prior work on optimal
multiprocessor Pfair or ERfair scheduling algorithms has been limited to synchronous periodic task systems.


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


Collections: Computer Technologies and Information Sciences