Utility Aware Snoozy Caches for Energy Efficient Chip Multi-Processors

Heavy leakage power consumption of on-chip last level caches (LLCs) has become the primary obstacle for architecting chip multi-processors (CMPs) in recent times. As leakage power has a direct relationship with the supply voltage, hence, periodic access profile based dynamic voltage scaling (DVS) in the LLC banks can be a promising option towards reducing this heavy cache leakage. A plethora of prior attempts have reduced this by anticipating working set size (WSS) of the applications and eventually putting some portions of the cache banks in low power mode. This proposed work aims to reduce leakage by putting a whole LLC bank into a low power (snoozy) mode through exploiting DVS at cache banks having minimal usages. Additionally, the resulting performance impacts of the low power snoozy mode are alleviated further by putting some snoozy banks in active mode on-demand. Experimental evaluations using full system simulation on a multi-banked 2MB 8-way set associative L2 cache show 10% more leakage savings on an average over a prior drowsy technique.