Summary: Early-Release Fair Scheduling
James H. Anderson and Anand Srinivasan
Department of Computer Science, University of North Carolina, Chapel Hill, NC 27599-3175
Phone: (919) 962-1757 Fax: (919) 962-1799 E-mail: fanderson,firstname.lastname@example.org
We present a variant of Pfair scheduling, which we call early-release fair (ERfair) scheduling. Like con-
ventional Pfair scheduling, ERfair scheduling algorithms can be applied to optimally schedule periodic tasks
on a multiprocessor system in polynomial time. However, ERfair scheduling di ers from Pfair scheduling in
that it is work conserving. As a result, average job response times may be much lower under ERfair schedul-
ing than under Pfair scheduling, particularly in lightly-loaded systems. In addition, runtime costs are lower
under ERfair scheduling. This is because, in Pfair-scheduled systems, signi cant bookkeeping information
is required to determine when a job of a task is and is not eligible for execution. In an ERfair system,
this bookkeeping information is not required because, once released, a job continues to be eligible until it
completes. To the best of our knowledge, ERfair scheduling is the rst truly work-conserving scheduling
discipline for periodic task systems that is optimal for multiprocessors.
Keyword: fairness, multiprocessors, optimality, Pfair, real-time scheduling, work-conserving schedulers.
Work supported by NSF grants CCR 9732916 and CCR 9972211. The rst author was also supported by an Alfred P. Sloan