Measurement-Based Probabilistic Timing Analysis (MBPTA) has consolidated as a technique to estimate probabilistic Worst-Case Execution Times (WCET) for critical software running on processors with high-performance hardware such as multilevel caches. Conventional random replacement (CRR) is the most suitable replacement policy for MBPTA due to its probabilistic nature: replacement choices are random and independent. CRR makes pathological replacement patterns probabilistic rather than systematic, though they can still occur. This paper proposes a new replacement policy, RPR, that keeps MBPTA compatibility and prevents CRR's pathological replacements in which addresses mapped to different cache lines randomly evict each other despite some lines in the same cache set are available. In particular, RPR maintains a higher degree of temporal locality than CRR. Our evaluation on a performance simulator (validated against a real industrial prototype) using the Mälardalen benchmarks and a railway case study shows that RPR delivers both high average performance (within 1% of LRU's performance) and tight WCET estimates 16% and 24% (for the case study and Mälardalen respectively) lower than those of CRR.

Peer Reviewed