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

Korean Institute of Information Scientists and Engineers (한국정보과학회)
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A Jitter Analysis for Improved Schedulability of Distributed Real-Time Tasks

분산 실시간 태스크의 스케쥴가능성 개선을 위한 지터 분석

  • 김태웅 (서울대학교 컴퓨터공학과) ;
  • 신현식 (서울대학교 컴퓨터공학과) ;
  • 장래혁 (서울대학교 컴퓨터공학과)
  • Published : 2000.05.15
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Abstract

In distributed real-time system, a task activated by the completion of its preceding task can be modeled as a periodic task with activation jitter. An activation jitter of a task is defined asthe difference between the worst case and the best case response time of its preceding task. Becausethe existing approaches assume that the best case response time is much smaller than the actual one,the activation jitter and the worst case response time of lower priority tasks are overestimated. Thispaper proposes a new analysis technique to calculate the best case response time more precisely andto reduce the activation jitter bounds. The proposed technique obtains the best case response time byconsidering the relative phase between tasks. The precise analysis of the activation jitters can reducethe worst case response time of other tasks and increase the schedulability. The simulation resultsshow that the proposed analysis technique improves the accuracy of the best case and the worst caseresponse time up to 40% and 6%, respectively.

분산 실시간 시스템에서 선행 태스크의 완료에 의해 활성화되는 태스크는 활성화 지터를 갖는 주기적 태스크로 모델링될 수 있다. 태스크의 활성화 지터는 선행 태스크의 최악과 최선 응답사간의 차로 정의된다. 기존의 방법은 최선 응답사간을 실제보다 훨씬 작은 값으로 가정하기 때문에, 활성화 지터와 낮은 우선순위를 갖는 태스크들의 최악 응답시간이 과대평가된다. 본 논문은 최선 응답사간을 보다 정확하게 산정하고 활성화 지터의 한계를 줄이기 위해 새로운 최선 응답시간 분석기법을 제안한다. 제안된 기법은 태스크들간의 상대적 위상을 고려하여 최선 응답시간을 구한다. 활성화 지터의 정확한 분석은 다른 태스크들의 최악 응답시간을 감소시키고 스케쥴가능성을 증가시킨다. 모의실험의 결과는 제안된 분석 기법이 최선 응답시간과 최악 응답시간의 정확도를 각각 최대 40%와 6%로 개선함을 보여 준다.

Keywords

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