WCET analysis of multi-level non-inclusive set-associative instruction caches

With the advent of increasingly complex hardware in real-time embedded systems (processors with performance enhancing features such as pipelines, cache hierarchy, multiple cores), many processors now have a set-associative L2 cache. Thus, there is a need for considering cache hierarchies when validating the temporal behavior of real-time systems, in particular when estimating tasks' worst-case execution times (WCETs). In this paper, we propose a safe static instruction cache analysis method for multi-level non-inclusive caches. The proposed method is experimented on medium-size and large programs. We show that the method is reasonably tight. We further show that in all cases WCET estimations are much tighter when considering the cache hierarchy than when considering only the LI cache. An evaluation of the analysis time is conducted, demonstrating that analyzing the cache hierarchy, has a reasonable computation time.