Instruction - based Reuse Distance Prediction Replacement Policy

— This paper presents a new cache replacement policy based on Instruction-based Reuse Distance Prediction (IbRDP) Replacement Policy originally proposed by Keramidas, Petoumenos, and Kaxiras [5] and further optimized by Petoumenos et al. [6]. In these works [5,6] we have proven that there is a strong correlation between the temporal characteristics of the cache blocks and the access patterns of instructions (PCs) that touch these cache blocks. Based on this observation we introduced a new class of instruction-based predictors which are able to directly predict with high accuracy at run-time when a cache block is going to be accessed in the future, a.k.a. the reuse distance of a cache block. Being able to predict the reuse distances of the cache blocks permits us to make near-optimal replacement decisions by " looking into the future. " In this work, we employ an extension of the IbRDP Replacement policy [6]. We carefully redesign the organization as well as the functionality of the predictor and the corresponding replacement algorithm in order to fit into the tight area budget provided by the CRC committee [3]. Since our proposal naturally supports the ability to victimize the currently fetched blocks by not caching them at all in the cache (Selective Caching), we submit for evaluation two versions: the base-IbRDP and the IbRDP enhanced with Selective Caching (IbRDP+SC). Our performance evaluations based on a subset of SPEC2006 applications show that IbRDP achieves an IPC improvement of 4.66% (arithmetic average) over traditional LRU, while IbRDP+SC is able to further increase its distance compared to the baseline LRU to 6.04%. Finally, we also show that IbRDP outperforms the previous state of the art proposal (namely Dynamic Insertion Policy or DIP [7]) by 2.32% in terms of IPC (3.81% for the IbRDP+SC).