Chapter 3: Dependability Benchmark Real Time Kernels in ...

Chapter 3:
Dependability Benchmark Real Time
Kernels in Onboard Space Systems




Abstract
In space real-time systems, correctness of operation depends not only on the right results
being generated but also on the results being generated within certain time constraints. With
the increased use of COTS Real-Time Kernels (RTK) in embedded systems the need for
assuring a high dependability level of such kernels also arose. Among several dependability
attributes, the determinism of the response time of RTK services, even in presence of faults,
is of paramount importance for hard real-time systems. This is particularly true for onboard
space systems that are more exposed to external disturbances such as radiation.
The benchmark presented in this chapter is targeted for onboard space systems. It aims to
allow integrators/developers to compare different RTKs with respect to their ability to
provide their services within the expected time frame. The benchmark provides metrics for
characterizing this capability. The main measure provided is the Predictability which scores
a RTK vis-à-vis its system calls response time fitting within its specification.

DBench Dependability Benchmark for Real Time Kernels in Onboard Space Systems
3.1 Introduction
In real-time systems correctness of operation depends not only on the accuracy of the results
provided but also on the results being produced within certain time constraints imposed by
the system ...