Optimal Configuration for Multiversion Real-Time Systems Using Slack Based Schedulability

Sayuri TERADA  Toshimitsu USHIO  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E93-A   No.12   pp.2709-2716
Publication Date: 2010/12/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E93.A.2709
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Theory of Concurrent Systems and its Applications)
real-time systems,  EDF scheduling,  multiversion task model,  optimization,  

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In an embedded control system, control performances of each job depend on its latency and a control algorithm implemented in it. In order to adapt a job set to optimize control performances subject to schedulability, we design several types of control software for each job, which will be called versions, and select one version from them when the job is released. A real-time system where each job has several versions is called a multiversion real-time system. A benefit and a CPU utilization of a job depend on the versions. So, it is an important problem to select a version of each job so as to maximize the total benefit of the system subject to a schedulability condition. Such a problem will be called an optimal configuration problem. In this paper, we assume that each version is specified by the relative deadline, the execution time, and the benefit. We show that the optimal configuration problem is transformed to a maximum path length problem. We propose an optimal algorithm based on the forward dynamic programming. Moreover, we propose sub-optimal algorithms to reduce computation times. The efficiencies of the proposed algorithms are illustrated by simulations.