Abstract: Persistent memory (PM) allows file systems to directly persist data on the memory bus. To increase the capacity of PM file systems, building a file system across sockets with each attached PM is attractive. However, accessing data across sockets incurs impacts of the non-uniform memory access (NUMA) architecture, which will lead to significant performance degradation. In this paper, we first use experiments to understand the NUMA impacts on building PM file systems. And then, we propose four design principles for building a high-performance PM file system NapFS for the NUMA architecture. We architect NapFS with per-socket local PM file systems and per-socket dedicated IO thread pools. This not only allows applications to delegate data accesses to IO threads for avoiding remote PM accesses, but also fully reuses existing single-socket PM file systems to reduce implementation complexity. Additionally, NapFS utilizes fast DRAM to accelerate performance by adding a global cache and adopts a selective cache mechanism to eliminate the redundant double-copy overhead for synchronization operations. Lastly, we show that NapFS can adopt extended optimizations to improve scalability and the performance of critical requests. We evaluate NapFS against other multi-socket PM file systems. The evaluation results show that NapFS achieves 2.2x and 1.0x throughput improvement for Filebench and RocksDB, respectively.