Global Priority Table for Last-Level Caches

Last-level caches (LLC) grow large with significant power consumption. As LLC´s capacity increases, it becomes quite inefficient. As recent studies show, a large percent of cache blocks are dead during the cache time. There is a growing need for LLC management to reduce the number of dead block in the LLC. However, there is a significant power requirement for the dead block´s in-placement and replacement operations. In this paper, we introduce a global priority table predictor, a technique which is used for determining a cache block´s priority when it attempts to insert into the LLC. It is similar to previous predictors, such as reuse distance and dead block predictor. The global priority table is indexed by the hash value of the block address and stores the priority value of the associate cache block. The priority value can be used to drive a dead block replacement and bypass optimization. Through the priority table, a large number of dead blocks could be bypassed. It achieves an average reduction of 13.2% in the number of LLC miss for twenty single-thread workloads from the SPEC2006 suite and 29.9% for ten multi-programmed workloads. It also yields a geometric mean speedup of 8.6% for single-thread workloads and a geometric mean normalized weighted speedup of 39.1% for multi-programmed workloads.