Breeze: User-Level Access to Non-Volatile Main Memories for Legacy Software
Amirsaman Memaripour, Steven Swanson · 2018
Non-volatile main memory (NVMM) technologies, such as phase change memory and 3D XPoint, offer DRAM-like performance and byte-addressable access to persistent data. A wide range of applications (e.g., key-value stores and database systems) stand to benefit from the performance potential of these technologies. These potential benefits are greatest when applications can access memory directly via load/store instructions rather than conventional file-based interfaces. This approach presents several challenges. In particular, applications need guaranteed consistency and safety semantics to protect their data structures in the face of system failures and programming errors. Implementing data structures that meet these requirements is challenging and error-prone. Researchers have proposed several libraries and programming language extensions that simplify this task, but, to date, all the proposed solutions either require pervasive changes to existing software or rely on special hardware support. As a result, porting legacy applications to leverage NVMM is likely to be prohibitively difficult and time consuming. We propose Breeze, a NVMM toolchain that minimizes the changes necessary to enable legacy code to reap the benefits of directly accessing NVMM. Breeze guarantees data consistency and validity of persistent pointers regardless of failures. The toolchain transparently detects and logs writes to NVMM and provides a simple mechanism for identifying atomic sections while avoiding complications common in previous systems such as special persistent pointer types. Porting Memcached and MongoDB to use Breeze only requires changes to 5% of the source code compared to 7-14% for NVML and NVM-Direct. Breeze also provides equal or superior performance compared to NVML and NVM-Direct, outperforming them by up to 10x.