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Journal of Scheduling

, Volume 7, Issue 2, pp 133–147 | Cite as

Best-Case Response Times and Jitter Analysis of Real-Time Tasks

  • Reinder J. Bril
  • Elisabeth F.M. Steffens
  • Wim F.J. Verhaegh
Article

Abstract

In this paper, we present a simple recursive equation and an iterative procedure to determine the best-case response times of periodic tasks under fixed-priority preemptive scheduling and arbitrary phasings. The approach is of a similar nature as the one used to determine worst-case response times (Joseph and Pandya, 1986) in the sense that where a critical instant is considered to determine the latter, we base our analysis on an optimal instant. Such an optimal instant occurs when all higher priority tasks have a simultaneous release that coincides with the completion of an execution of the task under consideration. The resulting recursive equation closely resembles the one for worst-case response times. The iterative procedure is illustrated by means of a small example. Next, we apply the best-case response times to analyze jitter in distributed multiprocessor systems. To this end, we discuss the effect of the best-case response times on completion jitter, as well as the effect of release jitter on the best-case response times. The newly derived best-case response times generally result in tighter bounds on jitter, in turn leading to tighter worst-case response time bounds.

response time best case periodic tasks preemptive scheduling fixed priority critical instant optimal instant jitter real-time systems 

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Copyright information

© Kluwer Academic Publishers 2004

Authors and Affiliations

  • Reinder J. Bril
    • 1
  • Elisabeth F.M. Steffens
    • 1
  • Wim F.J. Verhaegh
    • 1
  1. 1.Philips Research LaboratoriesEindhovenThe Netherlands

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