Integration methods of main memory and file system management for non-volatile main memory and implications of file system structures

Abstract

Byte addressable non-volatile (NV) memory, such as STT-RAM, MRAM, and PCM, is the next generation memory that can be used as both main memory and secondary storage. While it can persistently store data without power supply, its access speed is comparable to DRAM. While there have been the active researches on its use for either main memory or secondary storage, these researches were conducted independently. This paper presents the integration methods of the main memory and file system management for NV memory, so that it can be used as both main memory and storage. The presented methods use a file system as their basis for the NV memory management; thus, the internal data structures of a file system can have impacts upon the performance of the integration methods. We implemented the proposed methods in the Linux kernel, and performed the evaluation on a system emulator. The evaluation results show that 1) the proposed methods can perform comparably to the existing DRAM memory allocator and significantly better than the page swapping, 2) their performance is affected by the internal data structures of a file system, and 3) the data structures appropriate for traditional hard disk drives do not always work effectively for byte addressable NV memory.