Persistent Memory Programming: Challenges and Solutions in Multiple Languages

Both Windows and Linux now contain support for Persistent Memory, an emerging non-volatile memory (NVM) technology. Persistent Memory is available today in the form of NVDIMMs and is expected to explode in capacity in the near future. Unlike other NVM technologies, such as SSDs, Persistent Memory provides a byte-addressable programming model, allowing direct memory access like DRAM, but retaining its contents across power loss. Technologies such as Intel’s 3D XPoint are expected to provide terabytes of NVM per CPU socket, with performance near DRAM speeds. The result offers applications a new tier for data placement in addition to the traditional memory and storage tiers: the persistent memory tier. While there are numerous ways for an OS to leverage Persistent Memory in a way that is transparent to the application, converting an application to be "persistent memory aware" will allow the highest performance benefit.

This tutorial will start with the basic SNIA NVM Programming Model used by operating systems to expose Persistent Memory to applications. We will walk through code examples showing how applications get access to Persistent Memory and we will pay special attention to safe programming practices such as flushing to persistence, atomic operations, and writing power-fail safe code. We will look at CPU instructions designed for atomic operations, cache flushing, and fencing, and how they interact with Persistent Memory.

Next, the tutorial will provide a brief survey of available libraries, compilers, and research in this area. We will then walk through some more complex examples of persistent memory programming in C, C++, and Java. Using the open source NVM Libraries from http://pmem.io we will show how to solve the common programming pain points and how the higher-level languages can help avoid common persistent memory programming mistakes.