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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 USA
Abstract
Pfair scheduling was proposed by Baruah, Cohen, Plaxton, and Varvel as a non-
work-conserving way of optimally and e∆ciently scheduling periodic tasks on a mul-
tiprocessor. In this paper, we introduce a work-conserving variant of Pfair schedul-
ing called \early-release" fair (ERfair) scheduling. We also present a new scheduling
algorithm called PD 2 and show that it is optimal for scheduling any mix of early-
release and non-early-release asynchronous, periodic tasks. In contrast, almost all
prior work on Pfair scheduling has been limited to synchronous systems. PD 2 is an
optimization of an earlier deadline-based algorithm of Baruah, Gehrke, and Plaxton
called PD; PD 2 uses a simpler tie-breaking scheme than PD to disambiguate equal
deadlines. We present a series of counterexamples that suggest that, in general, the
PD 2 tie-breaking mechanism cannot be simpli ed. In contrast to this, we show that
no tie-breaking information is needed on two-processor systems.
Key words: Asynchronous periodic tasks, ERfair, fairness, multiprocessors,
optimality, Pfair, real time, scheduling

  

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

 

Collections: Computer Technologies and Information Sciences