Brief Announcement: On Implementing Wear Leveling in Persistent Synchronization Structures

The last decade has witnessed an explosion of research on persistent memory, which combines the low access latency of dynamic random access memory (DRAM) with the durability of secondary storage. Intel’s implementation of persistent memory, called Optane, comes close to realizing the game-changing potential of persistent memory in terms of performance; however, it also suffers from limited endurance and relies on a proprietary wear leveling mechanism to mitigate memory cell wear-out. The traditional embedded approach to wear leveling, in which the storage device itself maps logical addresses to physical addresses, can be fast and energy-efficient, but it is also relatively inflexible and can lead to missed opportunities for optimization. An alternative school of thought, exemplified by "open channel" solid state drives (SSDs), delegates responsibility for wear leveling to software, where it can be tailored to specific applications. In this research, we consider a hypothetical hardware platform where the same paradigm is applied to the persistent memory device, and ask how the wear leveling mechanism can be co-designed with synchronization structures that generate highly skewed memory access patterns. Building on the recent work of Liu and Golab, we implement an improved wear leveling atomic counter by leveraging hardware transactional memory in a novel way. Our solution is close to optimal with respect to both space complexity and measured performance.