Evaluation Of Selective Spilling Policy For Capacity Sharing Of Private L2 Caches In Cmp Architectures

Recently, Chip Multi-Processors (CMP) is widely used in server computing, PC and even hand held devices. In CMPs, private L2 caches have potential benefits in future CMPs, e.g. small access latency, performance isolation, tile-friendly architecture and simple low bandwidth on-chip interconnect. But the major weakness of private cache is the higher cache miss rate caused by small private cache capacity. For some programs, private cache capacity is too small and they experience high L2 cache miss rate. But for other programs, it is too large and they use only small L2 cache capacity. To deal with this problem, private caches share capacity through spilling replaced blocks to other private caches. However, indiscriminate spilling can make capacity problem worse and influence performance negatively. They can pollute cache space and even consume interconnect bandwidth. This paper proposes Throttling Capacity Sharing (TCS) for effective Capacity sharing in private L2 caches. TCS determines whether to spill a replaced block by predicting reuse possibility, based on life time and reuse time. In out performance evaluation, TCS improves weighted speedup by 54.64%, 5.34% and 7.21% compared to non-spilling, Cooperative Caching with best spill probability (CC) and Dynamic Spill-Receive (DSR), respectively.