Reducing cache pollution of prefetching in a small data cache

The need for a low power, high performance embedded processor has grown at a very fast pace in recent years. Embedded processors require smaller cache size for low power system-on-a-chip consideration. Decreasing cache size leads to reduced power consumption because a smaller cache has less capacitance from the bit array size as well as smaller drivers in decoder or peripheral circuitry.. Unfortunately, performance also decreases due to a lower cache hit rate when the cache size becomes smaller. Recently, to improve the miss rate on a cache, many prefetching schemes have been introduced. However, on a small cache, prefetching schemes do not perform well because projected data replace the data that a processor will need in the future. This causes cache pollution, which degrades system performance. To overcome the cache pollution on a small cache, the paper introduces a new technique called "Fixed Prefetch Block" that integrates with the prefetching scheme. To evaluate the effectiveness of our scheme, extensive stimulations on SPEC95 integer benchmarks and Mediabench benchmarks suites were performed. Results from the simulations indicate that with our proposed technique, cache pollution can be reduced on a small set associative cache.