A Latency-Optimized and Energy-Efficient Write Scheme in NVM-Based Main Memory

Nonvolatile memory (NVM) technologies are promising candidates as the next-generation main memory due to high scalability and low energy consumption. However, the performance bottlenecks, such as high write latency and low cell endurance, still exist in NVMs. To address these problems, frequent pattern compression schemes have been widely used, which however suffer from the lack of flexibility and adaptability. In order to overcome these shortcomings, we propose a well-adaptive NVM write scheme, called dynamic frequent pattern compression (DFPC), to significantly reduce the amount of write units and extend the lifetime. Instead of only using static frequent patterns in existing FPC schemes, which are predefined and not always efficient for all applications, the idea behind DFPC is to exploit the characteristics of data distribution in execution to obtain dynamic patterns, which often appear in the real-world applications. To further improve the compression ratio, we exploit the value locality in a cache line to extend the granularity of dynamic patterns. Hence, DFPC can encode the contents of cache lines with more kinds of frequent data patterns. Moreover, to further support efficient write and read operations in the context of multilevel/triple-level cell NVMs, we need to extend the DFPC to improve performance in terms of the access latency and energy consumption. We hence propose a latency-optimized and energy-efficient compression write scheme to encode the compressed data with low energy and latency states, i.e., enhanced DFPC, thus reducing the latency and energy consumption. We implement DFPC in GEM5 with NVMain and execute the applications from SPEC CPU2006 to evaluate our scheme. Experimental results demonstrate the efficacy and efficiency of DFPC. We have released the source codes for public use at Github https://github.com/dfpcscheme/DFPCScheme.