Introductory Materials

This USENIX ;login: article, published in the Summer of 2017, provides an overview of the persistent memory programming model and the related software work that has been taking place. It includes a very high-level description of programming with PMDK, although it refers to it by the old name, NVM Libraries. This article is actually a follow-on to an earlier article, published in the Summer 2013 issue of USENIX ;login:.

The projects on this site, like PMDK, are product-neutral, meant to work on any product that provides the persistent memory programming model. One such product is Intel’s 3D XPoint. Intel has assembled a collection of persistent memory programming documentation, webinars, videos, and related materials on the Intel Developer Zone.

Dozens of companies have collaborated on a common persistent memory programming model in the SNIA NVM Programming Technical Workgroup (TWG). SNIA provides a persistent memory page on their web site with links to recent presentations, persistent memory standards and white papers, etc. The SNIA activity continues to be very active, working on areas like remote persistent memory and security. The original programming model specification put forward the basic idea that applications access persistent memory as memory-mapped files, a concept which has appeared as the DAX feature (short for Direct Access) on both Linux and Windows.

Standards

The SNIA NVM Programming Model standard describes the basic programming model used for persistent memory programming.

The ACPI Specification, starting with version 6.0, defines the NVDIMM Firmware Interface Table (NFIT) which is how the existence of persistent memory is communicated to operating systems. The specification also describes how NVDIMMs are partitioned into namespaces, methods for communicating with NVDIMMs, etc.

The UEFI Specification, covers other NVDIMM-related topics such as the Block Translation Table (BTT) which allows an NVDIMM to provide block device semantics.

Before the above two standards were developed, the NVDIMM Namespace Specification [pdf] described the namespace and BTT mechanisms. The link to the outdated document is maintained here for reference.

The NVDIMM Driver Writers Guide [pdf] is targeted to driver writers for NVDIMMs that adhere to the NFIT tables in the Advanced Configuration and Power Interface (ACPI) V6.0 specification, the Device Specific Method (DSM) specification and the NVDIMM Namespace Specification. This document specifically discusses the block window HW interface and persistent memory interface that Intel is proposing for NVDIMMs. A version of the document with change bars [pdf] from the previous version is also available.

The NVDIMM DSM Interface [pdf], Version 1.6, is targeted to writers of BIOS and OS drivers for NVDIMMs whose design adheres to the NFIT Tables in the ACPI specification. The document specifically discusses the NVDIMM Device Specific Method (_DSM) example.