Utilization Based Schedulability Bounds for Age Constraint Process Sets in Real-Time Systems

  • Authors:

  • Lars Lundberg

  • Affiliations:

  • Department of Computer Science, Blekinge Institute of Technology, S-372 25 Ronneby, Sweden Lars.Lundberg@bth.se

  • Venue:
  • Real-Time Systems
  • Year:
  • 2002

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Abstract

Some real-time systems consist of a number of processes that operate under age constraints. In such systems, the maximum time from the start of process Li in cycle k to the end in cycle k+1 must not exceed the age constraint Ai for that process. The age constraint can be met by using fixed priority scheduling and periods equal to Ai/2. However, this approach restricts the number of process sets which are schedulable. In this paper, we define a method for obtaining process periods other than Ai/2. The periods are calculated in such a way that the age constraints are met. Our approach is better in the sense that a larger number of process sets can be scheduled compared to using periods equal to Ai/2. The main results in this paper are a number of performance bounds on age constraint processes. These bounds show that there is a significant gain in worst case as well as in best case behavior by using periods other than Ai/2, particularly when there are a large number of processes in the system.