Summary: Efficient Object Sharing in Quantum­Based Real­Time
Systems \Lambda
James H. Anderson, Rohit Jain, and Kevin Jeffay
Department of Computer Science
University of North Carolina
Chapel Hill, NC 27599­3175
Phone: (919) 962­1757
Fax: (919) 962­1799
E­mail: fanderson,jain,jeffayg@cs.unc.edu
May 1998
Abstract
We consider the problem of implementing shared objects in uniprocessor and multiprocessor real­time
systems in which tasks are executed using a scheduling quantum. In most quantum­based systems, the size
of the quantum is quite large in comparison to the length of an object call. As a result, most object calls can
be expected to execute without preemption. A good object­sharing scheme should optimize for this expected
case, while achieving low overhead when preemptions do occur. Our approach is to use an optimistic retry
scheme coupled with the assumption that each task can be preempted at most once across two object calls.
Given this preemption assumption, each object call can be retried at most once. Experimental evidence is
cited that suggests that for most quantum­based systems, our preemption assumption is reasonable. Major
contributions of this paper include several new retry­based shared­object algorithms for uniprocessors and

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

Collections: Computer Technologies and Information Sciences