Journal of KIISE:Computer Systems and Theory (한국정보과학회논문지:시스템및이론)

Korean Institute of Information Scientists and Engineers (한국정보과학회)
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A Period Assignment Algorithm for Real-Time System Design

실시간 시스템 설계를 위한 주기 할당 알고리즘

  • Published : 2000.01.15
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Abstract

Digital controllers found in many industrial real-time systems consist of a number of interacting periodic tasks. To sustain the required control quality, these tasks possess the maximum activation periods as performance constraints. An essential step in developing a real-time system is thus to assign each of these tasks a constant period such that the maximum activation requirements are met while the system utilization is minimized [1]. Given a task graph design allowing producer/consumer relationships among tasks [2], resource demands of tasks, and range constraints on periods, the period assignment problem falls into a class of nonlinear optimization problems. This paper proposes a ploynomial time approximation algorithm which produces a solution whose utilization does not exceed twice the optimal utilization. Our experimental analysis shows that the proposed algorithm finds solutions which are very close to the optimal ones in most cases of practical interest.

산업용 실시간 시스템에서 사용되는 디지털 제어기는 상호 작용하는 주기적 태스크들로 이루어져 있다. 이러한 태스크들은 최대 수행 주기 (maximum activation periods)를 제약조건으로 가짐으로써, 요구되는 제어특성을 유지한다. 그러므로 실시간 시스템을 개발하는데 있어 필수적인 단계는 각각의 태스크에 게 자원 이용률을 최소화하면서 최대 수행 조건을 만족시킬 수 있는 고정된 주기를 할당하는 것이다.[1] 각각의 태스크간의 생산자/소비자(producer/consumer)관계를 나타내주는 태스크 그래프와 자원 요구량, 그리고 주기에 대한 범위제한이 주어진다면 주기 할당 문제는 비선형 최적화 문제가 된다. 이 논문에서는 최적해의 자원이용률의 두 배를 넘지 않는 해를 찾을 수 있는 선형 수행시간의 근사 알고리즘을 제시한다. 실험 결과에서 알 수 있듯이, 제안된 알고리즘은 대부분의 경우 최적해에 매우 근접한 해를 가지게 된다.

Keywords

References

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