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Fair Scheduling of Real-time Tasks on Multiprocessors James Anderson, Philip Holman, and Anand Srinivasan
 

Summary: Fair Scheduling of Real-time Tasks on Multiprocessors
James Anderson, Philip Holman, and Anand Srinivasan
Department of Computer Science, University of North Carolina at Chapel Hill
1 Introduction
There has been much recent interest in fair scheduling algorithms for real-time multiprocessor
systems. The roots of much of the research on this topic can be traced back to the seminal work
of Baruah et al. on Proportionate fairness (Pfairness) [6]. This work proved that the problem of
optimally scheduling periodic tasks1 on multiprocessors could be solved on-line in polynomial time
by using Pfair scheduling algorithms. Pfair scheduling differs from more conventional real-time
scheduling approaches in that tasks are explicitly required to execute at steady rates. In most real-
time scheduling disciplines, the notion of a rate is implicit. For example, in a periodic schedule, a
task T executes at a rate defined by its required utilization (T.e/T.p) over large intervals. However,
T's execution rate over short intervals, e.g., individual periods, may vary significantly. Hence, the
notion of a rate under the periodic task model is a bit inexact.
Under Pfair scheduling, each task is executed at an approximately uniform rate by breaking it
into a series of quantum-length subtasks. Time is then subdivided into a sequence of (potentially
overlapping) subintervals of approximately equal lengths, called windows. To satisfy the Pfairness
1
A periodic task T is characterized by a phase T., an execution requirement T.e, and a period T.p: a job release
(i.e., task invocation) occurs at time T. + (k - 1) T.p for each integer k 1 and the kth

  

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

 

Collections: Computer Technologies and Information Sciences