Towards a Better Cache Utilization Using Controlled Cache Partitioning

Abstract

Many multi-core processors nowadays employ a shared Last Level Cache (LLC). Partitioning LLC becomes more important as LLC is shared among the cores. Past research has demonstrated that the traditional least recently used (LRU) based partitioning cum replacement policy has adverse effects on parameters like instruction per cycle (IPC), miss rate and speedup. This leads to poor performance in an environment when multiple cores compete for one global LLC. Applications, enjoying locality of reference are purely benefited by LRU, however LRU fails for the applications showing working set size (WSS) large than the LLC size. In this work, we propose a scheme which allows cores to steal/donate their lines upto a threshold and give them a chance to adjust their partition when there is a miss. Instead of maintaining strict target partitioning, we introduce a flexible threshold window. Our evaluation with multiprogrammed workloads shows significant performance improvement.