A Dynamic Link-latency Aware Cache Replacement Policy (DLRP)

Abstract

Multiprocessor system-on-chips (MPSoCs) in modern devices have mostly adopted the non-uniform cache architecture (NUCA) [1], which features varied physical distance from cores to data locations and, as a result, varied access latency. In the past, researchers focused on minimizing the average access latency of the NUCA. We found that dynamic latency is also a critical index of the performance. A cache access pattern with long dynamic latency will result in a significant cache performance degradation without considering dynamic latency. We have also observed that a set of commonly used neural network application kernels, including the neural network fully-connected and convolutional layers, contains substantial accessing patterns with long dynamic latency. This paper proposes a hardware-friendly dynamic latency identification mechanism to detect such patterns and a dynamic link-latency aware replacement policy (DLRP) to improve cache performance based on the NUCA. The proposed DLRP, on average, outperforms the least recently used (LRU) policy by 53% with little hardware overhead. Moreover, on average, our method achieves 45% and 24% more performance improvement than the not recently used (NRU) policy and the static re-reference interval prediction (SRRIP) policy normalized to LRU.