Cheetah: An Adaptive User-Space Cache for Non-volatile Main Memory File Systems

Over the past decade, most NVMM file systems have been designed without detailed knowledge of real NVDIMMs. With the release of Intel Optane DC Persistent Memory, researchers find that the performance characteristics of real NVMM differ a lot from their expectations. The design decisions they made lead to limited scalability, significant software overhead, and severe write amplification. We present Cheetah, a user-level cache designed for existing NVMM file systems to improve overall performance. Cheetah leverages the unique characteristics of Intel Optane DC persistent memory to design a fine-grained data block allocation policy in order to reduce write amplification. To minimize the impact of the long write latency of NVMM, Cheetah absorbs asynchronous writes in DRAM rather than NVMM. Our experimental results show that Cheetah provides up to 3.5x throughput improvement compared to the state-of-the-art NVMM file systems in write-intensive workloads.