Enabling Reliable Memory-Mapped I/O with Auto-snapshot for Persistent Memory Systems

Persistent memory (PM) is promising to be the next-generation storage device with better I/O performance. Since traditional I/O path is too lengthy to drive PM featuring low latency and high bandwidth, prior works proposed memory-mapped I/O (MMIO) to shorten the I/O path to PM. However, native MMIO directly maps files into the user address space, which puts files at risk of being corrupted by scribbles and non-atomic I/O interfaces, causing serious reliability issues. To address these issues, we propose RMMIO, an efficient user-space library that provides reliable MMIO for PM systems. RMMIO provides atomic I/O interfaces and lightweight snapshots to ensure the reliability of MMIO. Compared with existing schemes, RMMIO mitigates additional writes and extra software overheads caused by reliability guarantees, thus achieving MMIO-like performance. In addition, we also propose an automatic snapshot with efficient memory management for RMMIO to minimize data loss incurred by reliability issues. The experimental results of microbenchmarks show that RMMIO achieves 8.49x and 2.31x higher throughput than ext4-DAX and the state-of-the-art MMIO-based scheme, respectively, while ensuring data reliability. The real-world application accelerated by RMMIO achieves at most 7.06x higher throughput than that of ext4-DAX.