Designing an efficient persistent in-memory file system

As the emerging technologies of persistent memory, such as MRAM, PCM, etc., provide opportunities for connecting persistent memory to main memory bus directly, file system structure needs re-studying and re-designing. This paper presents a new design of persistent, in-memory file system for computers systems employing persistent memory. We introduce a novel design framework based on the concept that each file has its own "File Virtual Address Space". Following this idea, address mapping of file data access can be efficiently handled by address translation hardware. The new design pushes the boundary of persistent, in-memory file system to such an extent that software layers in I/O stack are bypassed. File data can be read continuously without interrupt or traversing metadata structure. The proposed file system, called Sustainable In-Memory File System (SIMFS), is implemented in Linux. Extensive experiments have been conducted, showing that the throughput of SIMFS approaches the memory bus bandwidth in best cases. Comparing with other in-memory file systems, SIMFS reaches 50-80 times, 5 times, and 1.1-1.6 times faster than PRAMFS, EXT4 on Ramdisk, and PMFS, respectively. To the authors' knowledge, SIMFS gives the best known results in literature.