Configurable cache subsetting for fast cache tuning

Numerous variations of configurable caches, having variable parameters like total size, line size, and associativity, have been proposed in commercial microprocessors in recent years. Tuning a configurable cache to a target application has been shown to reduce memory-access power by over 50%. However, searching the configuration space for the best configuration can require much time or power, even when using recent cache tuning heuristics. We sought to determine, for a particular domain of applications, the smallest subset of cache configurations that would still enable effective tuning. For a suite of 34 benchmarks and a cache with 18 possible configurations, we determine through an exhaustive search of all possible subsets, that only 3 or 4 candidate configurations are necessary to support tuning. We introduce a new heuristic, adapted from an efficient and effective heuristic developed for data mining, to quickly determine the best configurations for any sized subset, with near optimal results. We then consider a configurable cache with 17,640 possible configurations and improve our heuristic to include a pre-pruning step, yielding near optimal tuning results. We conclude that only 3 or 4 possible cache configurations are needed to offer a near optimal configuration for every benchmark in our suite - resulting in a 91% reduction in design space exploration time over a state-of-the-art cache tuning heuristic.