Using a Local Prefetch Strategy to Obtain Temporal Time Predictability

Abstract

Today's embedded systems are considering cache as inherent part of their design. Unfortunately, cache memory behavior heavily depends on the past references which model a large execution history and makes WCET analysis impractical. This paper presents a novel prefetch memory mechanism that simplifies the prediction of cache hits/misses because the memory access times are independent of the execution history. We use local prefetching into on-chip memory together with a custom-designed prefetch controller instead of cache memories to provide for time-predictable memory accesses. To be competitive in code execution time, our approach relies on a special organization of main memory and on a modified compiler that generates code layouts to allow for parallel prefetching from different memory banks. The proposed solution is still in a conceptual phase. The paper discusses design decisions and parameters to be explored.