Optimizing synchronization mechanism for block-based file systems using persistent memory

Existing block-based file systems employ buffer caching mechanism to improve performance, which may result in data loss in the case of power failure or system crash. To avoid data loss, the file systems provide synchronization operations for applications to synchronously write the dirty data in DRAM cache back to the slow block devices. However, the synchronization operations can severely degrade the performance of the file system since violating the intention of buffer caching mechanism. In this paper, we propose to relieve the overhead of synchronization operations while ensuring data reliability by utilizing a small Persistent Memory. The proposed Persistent Memory assisted Write-back (PMW) mechanism includes a dedicated Copy-on-Write mechanism to guarantee data consistency and a write-back mechanism across PM and the block devices. We implement the proposed PMW in Linux kernel based on Ext4. The experimental results show that PMW can achieve about 2.2× and 1.6× performance improvement over the original Ext4 and AFCM, the state-of-the-art PM-based synchronization mechanism, on the TPCC workload, respectively.