High-Endurance Hybrid Cache Design in CMP Architecture With Cache Partitioning and Access-Aware Policies

Abstract

In recent years, nonvolatile memory (NVM) technologies, such as spin-transfer torque random-access memory (RAM) (STT-RAM) and phase change RAM, have drawn a lot of attention due to their low leakage and high density. However, both of these NVMs suffer from high write latency and limited endurance problems. To mitigate the write pressure on NVM, many static RAM (SRAM)/NVM hybrid cache designs have been proposed with write management policies. Unfortunately, existing hybrid cache designs do not consider the unbalanced workload of each core in (chip multiprocessor) architecture, resulting in unbalanced wear out of hybrid caches. This paper considers the unbalanced write distribution of a hybrid cache for CMP architecture as well as a novel hybrid cache design that includes SRAM cache, STT-RAM cache, and STT-RAM/SRAM hybrid cache banks. Based on the proposed hybrid cache design, two access-aware policies are proposed to mitigate unbalanced wearout of the STT-RAM region, and a wearout-aware dynamic cache partitioning scheme is proposed to dynamically partition the hybrid cache, improving the unbalanced write pressure among different cache partitions. The experimental results show that our proposed scheme and policies can achieve an average of 89 times improvement in cache lifetime and are able to reduce energy consumption by 58% compared with a SRAM cache.