Improving inclusive cache performance with two-level eviction priority

Inclusive cache hierarchies are widely adopted in modern processors, since they can simplify the implementation of cache coherence. However, it sacrifices some performance to guarantee inclusion. Many recent intelligent management policies are proposed to improve the last-level cache (LLC) performance by evicting blocks with poor locality earlier. Unfortunately, they are inapplicable in inclusive LLCs. In this paper, we propose Two-level Eviction Priority (TEP) policy. Besides the eviction priority provided by the baseline replacement policy, TEP appends an additional high level of eviction priority to LLC blocks, which is decided at the insertion time and cannot be changed during their lifetime in the LLC. When blocks with high eviction priority are not in inner caches anymore, they get evicted from the LLC preferentially. Thus, the LLC can retain more useful blocks to improve performance. TEP can cooperate well with various baseline replacement policies. Our evaluation shows that TEP with NRU can improve the performance of inclusive LLCs significantly while requiring negligible extra storage. It also outperforms other recent proposals including QBS, DIP, and DRRIP.