UFLRU: Unmapped File First LRU Scheme for Non-volatile Memory

Abstract

Nonvolatile memory, which exhibits low I/O latency and guarantees persistency of data, is considered as a new memory that is going replace the volatile memory. Since the nonvolatile memory has a smaller capacity than NAND Flash memory or hard disk drives, nonvolatile memory requires a swap partition on a storage device to free the limited resources for other applications. Most of the existing swap algorithms use a page replacement policy optimized for volatile memory; however, the algorithms do not take the characteristics of the nonvolatile memory into account. Thus, there are irrelevant or unnecessary operations for the nonvolatile memory, thereby reducing the overall performance of the system. In this paper, we develop UFLRU (Unmapped object First LRU) swap algorithm that is optimized for the nonvolatile memory. We evaluate the swap out and in performance of FIFO, SCLRU, CFLRU, and UFLRU. The result shows that UFLRU is 30%, 25%, and 15% better than FIFO, SCLRU, and CFLRU in performing swap out, respectively; for swap in, UFLRU shows 35%, 55%, and 28% better performance than the FIFO, SCLRU, and CFLRU, respectively.