On predictability of caches for real-time applications

This paper studies the effects of hit ratio on the timing predictability of real-time tasks based on trace driven simulation. The impact on execution times of the variance of the hit ratio for different program runs is studied, covering a wide range of cache sizes and organizations. An analytical expression to quantify the timing predictability is derived, so that timing errors due to variations of the hit ratio con be bounded. Based on this result, we derived the upper bound for the worst-case execution time (WCET) when using caches. Using the WCET bounds, some experimental results are presented on the performance impact on hard real-time systems of different cache sizes and organizations