Impact of Partitioning Cache Schemes on the Cache Hierarchy of SMT Processors

Power consumption is becoming an increasingly important component of processor design. As technology node shrinks both static and dynamic power become more relevant. This is particularly critical for the cache hierarchy. Previous implementations mainly focus on reducing only one kind of power in the cache, either static or dynamic. However, for a more robust approach that will remain relevant as technology continues to shrink, both aspects of power need to be addressed. Recent processors, e.g. Intel Core or IBM Power8, implement simultaneous multithreading (SMT) cores to hide high memory latencies. In these systems, the dynamic energy in the L1 cache is even more stressed since this cache level is shared by several threads running on the same core. This paper proposes and evaluates the use of phase adaptive caches in all structures of a 3-level cache hierarchy of a SMT cores. Compared to the use of conventional caches, our work results on significant dynamic and leakage energy savings with scarce performance impact.