Nap: Persistent Memory Indexes for NUMA Architectures

We present Nap, a black-box approach that converts concurrent persistent memory (PM) indexes into non-uniform memory access (NUMA)-aware counterparts. Based on the observation that real-world workloads always feature skewed access patterns, Nap introduces a NUMA-aware layer (NAL) on the top of existing concurrent PM indexes, and steers accesses to hot items to this layer. The NAL maintains (1) per-node partial views in PM for serving insert/update/delete operations with failure atomicity and (2) a global view in DRAM for serving lookup operations. The NAL eliminates remote PM accesses to hot items without inducing extra local PM accesses. Moreover, to handle dynamic workloads, Nap adopts a fast NAL switch mechanism. We convert five state-of-the-art PM indexes using Nap. Evaluation on a four-node machine with Optane DC Persistent Memory shows that Nap can improve the throughput by up to 2.3× and 1.56× under write-intensive and read-intensive workloads, respectively.