Open Access

Reclaiming Spare Capacity and Improving Aperiodic Response Times in Real-Time Environments

EURASIP Journal on Embedded Systems20112011:391215

DOI: 10.1155/2011/391215

Received: 30 August 2010

Accepted: 28 January 2011

Published: 16 March 2011

Abstract

Scheduling recurring task sets that allow some instances of the tasks to be skipped produces holes in the schedule which are nonuniformly distributed. Similarly, when the recurring tasks are not strictly periodic but are sporadic, there is extra processor bandwidth arising because of irregular job arrivals. The additional computation capacity that results from skips or sporadic tasks can be reclaimed to service aperiodic task requests efficiently and quickly. We present techniques for improving the response times of aperiodic tasks by identifying nonuniformly distributed spare capacity—because of skips or sporadic tasks—in the schedule and adding such extra capacity to the capacity queue of a BASH server. These gaps can account for a significant portion of aperiodic capacity, and their reclamation results in considerable improvement to aperiodic response times. We present two schemes: NCLB-CBS, which performs well in periodic real-time environments with firm tasks, and NCLB-CUS, which can be deployed when the basic task set to schedule is sporadic. Evaluation via simulations and implementation suggests that performance improvements for aperiodic tasks can be obtained with limited additional overhead.

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Authors’ Affiliations

(1)
Department of Electrical and Computer Engineering, the University of British Columbia
(2)
Department of Computer Science and Engineering, University of Nebraska-Lincoln

Copyright

© Gopalakrishnan and X. Liu. 2011

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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