Efficient Memory Mapped File I/O for In-Memory File Systems

Recently, with the emergence of low-latency NVM storage, software overhead has become a greater bottleneck than storage latency, and memory mapped file I/O has gained attention as a means to avoid software overhead. However, according to our analysis, memory mapped file I/O incurs a significant amount of additional overhead. To utilize memory mapped file I/O to its true potential, such overhead should be alleviated. We propose map-ahead, mapping cache, and extended madvise techniques to maximize the performance of memory mapped file I/O on lowlatency NVM storage systems. This solution can avoid both page fault overhead and page table entry construction overhead. Our experimental results show throughput improvements of 38–70% in microbenchmarks and performance improvements of 6–18% in real applications compared to existing memory mapped I/O mechanisms.