Failure-Dependent timing analysis - a new methodology for probabilistic worst-case execution time analysis

  • Authors:

  • Kai Höfig

  • Affiliations:

  • AG Software Engineering: Dependability, University of Kaiserslautern, Kaiserslautern, Germany

  • Venue:
  • MMB'12/DFT'12 Proceedings of the 16th international GI/ITG conference on Measurement, Modelling, and Evaluation of Computing Systems and Dependability and Fault Tolerance
  • Year:
  • 2012

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Abstract

Embedded real-time systems are growing in complexity, which goes far beyond simplistic closed-loop functionality. Current approaches for worst-case execution time (WCET) analysis are used to verify the deadlines of such systems. These approaches calculate or measure the WCET as a single value that is expected as an upper bound for a system's execution time. Overestimations are taken into account to make this upper bound a safe bound, but modern processor architectures expand those overestimations into unrealistic areas. Therefore, we present in this paper how of safety analysis model probabilities can be combined with elements of system development models to calculate a probabilistic WCET. This approach can be applied to systems that use mechanisms belonging to the area of fault tolerance, since such mechanisms are usually quantified using safety analyses to certify the system as being highly reliable or safe. A tool prototype implementing this approach is also presented which provides reliable safe upper bounds by performing a static WCET analysis and which overcomes the frequently encountered problem of dependence structures by using a fault injection approach.