Improving worst-case cache performance through selective bypassing and register-indexed cache

Mohamed Ismail, Daniel Lo, G. Edward Suh

Abstract: Worst-case execution time (WCET) analysis is a critical part of designing real-time systems that require strict timing guarantees. Data caches have traditionally been challenging to analyze in the context of WCET due to the unpredictability of memory access patterns. In this paper, we present a novel register-indexed cache structure that is designed to be amenable to static analysis. This is based on the idea that absolute addresses may not be known, but by using relative addresses, analysis may be able to guarantee a number of hits in the cache. In addition, we observe that keeping unpredictable memory accesses in caches can increase or decrease WCET depending on the application. Thus, we explore selectively bypassing caches in order to provide lower WCET. Our experimental results show reductions in WCET of up to 35% over the state-of-the-art static analysis.