Towards Transparent and Seamless Storage-As-You-Go with Persistent Memory

In traditional computer systems, memory and storage are statically divide and separately allocated. In such a strictly dichotomized system, resource usage becomes unbalanced; more memory is always in need, yet large portions of storage remains unused. The goal of this paper is to break this strict division of memory and storage, and present a system that can dynamically move the boundary between memory and storage as need be. Commercial Persistent Memory (PM) is now in the horizon. PM products based on the DIMM interface are expected to be available soon as well. In this paper, we assume a hybrid memory system composed of DRAM and DIMM interface PM, where the intention is to use PM as storage space. For such a system, we propose Storage-As-You-Go (SAY-Go), a system that transparently adjusts the use of PM such that PM can be used as memory as well as storage as need be. To this end, we present the design and implementation of Persistent Memory Buddy (PMB), a memory allocation service that can freely grow and shrink memory it is managing.