The impact of extrinsic cache performance on predictability of real-time systems

Cache memories are commonly avoided in real-time systems because of their unpredictable behavior. Recently, some research has been done to obtain tighter bounds on the worst case execution time of cached programs. These techniques usually assume a non preemptive underlying system. However, some techniques can be applied to allow the use of caches in preemptive systems. This paper compares methods for dealing with extrinsic cache behavior (inter-task cache interference). Time-domain oriented methods (the inter-task cache interference is incorporated in the schedulability analysis) are compared to space-domain oriented ones (increase of the cache predictability by assigning private cache partitions to tasks). The obtained results bound the applicability domain for each method for a variety of hardware and workload configurations. The results can be used as design guidelines