M-CLOCK: Migration-optimized page replacement algorithm for hybrid DRAM and PCM memory architecture

Phase Change Memory (PCM) has drawn great attention as a main memory due to its attractive characteristics such as non-volatility, byte-addressability, and in-place update. However, since the capacity of PCM is not fully mature yet, hybrid memory architecture that consists of DRAM and PCM has been suggested. In addition, page replacement algorithm based on hybrid memory architecture is actively being studied because existing page replacement algorithms cannot be used on hybrid memory architecture in that they do not consider the two weaknesses of PCM: high write latency and low endurance. In this paper, to mitigate the above hardware limitations of PCM, we revisit the page cache layer for the hybrid memory architecture. We also propose a novel page replacement algorithm, called M-CLOCK, to improve the performance of hybrid memory architecture and the lifespan of PCM. In particular, M-CLOCK aims to reduce the number of PCM writes that negatively affect the performance of hybrid memory architecture. Experimental results clearly show that M-CLOCK outperforms the state-of-the-art page replacement algorithms in terms of the number of PCM writes and effective memory access time by up to 98% and 34%, respectively.