Cache-Persistence-Aware Response-Time Analysis for Fixed-Priority Preemptive Systems

International audienceA task can be preempted by several jobs of higher priority tasks during its response time. Assuming the worst-case memory demand for each of these jobs leads to pessimistic worst-case response time (WCRT) estimations. Indeed, there is a big chance that a large portion of the instructions and data associated with the preempting task Tj are still available in the cache when Tj releases its next jobs. Accounting for this observation allows the pessimism of WCRT analysis to be significantly reduced, which is not considered by existing work. The four main contributions of this paper are: 1) The concept of persistent cache blocks is introduced in the context of WCRT analysis, which allows re-use of cache blocks to be captured,2) A cache-persistence-aware WCRT analysis for fixed-priority preemptive systems exploiting the PCBs to reduce the WCRT bound, 3) A multi-set extension of the analysis that further improves the WCRT bound and 4) An evaluation showing that our cache-persistence-aware WCRT analysis results in up to 10%higher schedulability than state-of-the-art approaches