WCET Analysis for Preemptive Scheduling

Abstract

Hard real-time systems induce strict constraints on the timing of the task
set. Validation of these timing constraints is thus a major challenge during the
design of such a system. Whereas the derivation of timing guarantees must
already be considered complex if tasks are running to completion, it gets even
more complex if tasks are scheduled preemptively -- especially due to 
caches, deployed to improve the average performance. In this paper we propose
a new method to compute valid upper bounds on a task's worst case execution time
(WCET). Our method approximates an optimal memory layout such that
the set of possibly evicted cache-entries during preemption is
minimized. This set then delivers information to bound the execution time of
tasks under preemption in an adopted WCET analysis.