ReD: A Policy Based on Reuse Detection for Demanding Block Selection in Last-Level Caches

In this paper, we propose a new block selection policy for Last-Level Caches (LLCs) that decides, based on Reuse Detection, whether a block coming from main memory is inserted, or not, in the LLC. The proposed policy, called ReD, is demanding in the sense that blocks bypass the LLC unless their expected reuse behavior matches specific requirements, related either to their recent reuse history or to the behavior of associated instructions. Generally, blocks are only stored in the LLC the second time they are requested in a limited time window. Secondarily, some blocks enter the LLC on the first request if their associated requesting instruction has shown to request highly-reused blocks in the past. ReD includes two table structures that allow tracking, measuring and correlating reuse for specific block addresses and requesting program counters within a constrained storage budget. It can be implemented on top of any other base replacement algorithm. Other parts of the base replacement policy, such as promotion or victim selection, can remain unchanged, enabling our policy to work along with many state-of-the-art replacement algorithms.