Optimizing File Systems on Heterogeneous Memory by Integrating DRAM Cache with Virtual Memory Management

This paper revisits the usage of DRAM cache in DRAM-PM heterogeneous memory file systems. With a comprehensive analysis of existing file systems with cache-based and DAXbased designs, we show that both suffer from suboptimal performance due to excessive data movement. To this end, this paper presents a cache management layer atop heterogeneous memory, namely FLAC, which integrates DRAM cache with virtual memory management. FLAC is further incorporated with two techniques called zero-copy caching and parallel-optimized cache management, which facilitates fast data transfer between file systems and applications as well as efficient data synchronization/migration between DRAM and PM. We further design and implement a library file system upon FLAC, called FlacFS. Micro benchmarks show that FlacFS provides up to two orders of magnitude performance improvement over existing file systems in file read/write. With real-world applications, FlacFS achieves up to 10.6 and 9.9 times performance speedup over state-of-the-art DAX-based and cache-based file systems, respectively.