关键词: 持久性内存, 多核架构, 键值系统, 并发控制, 崩溃一致性

Abstract: Compared with traditional memory, i.e., DRAM, persistent memory has the characteristics of large capacity and non-volatility, which brings new opportunities for building large-scale persistent memory key-value store systems. However, designing a persistent memory key-value store under a multicore server architecture faces many challenges, including CPU cache thrash due to concurrency control, the consumption and competition of limited write bandwidth for persistent memory, and aggravated conflicts between threads caused by high latency of persistent memory. In this paper, MPKV, a multicore-friendly persistent memory key-value store is proposed. By designing efficient concurrency control methods and reducing write operations to persistent memory, the system’s multicore concurrency performance is fully improved. To avoid the extra persistent memory write bandwidth consumption caused by lock resources, MPKV introduces a volatile lock management mechanism to separate write lock resources from indexes and maintain them separately in DRAM. To ensure crash consistency and improve concurrent query performance, MPKV introduces a two-phase atomic write mechanism, which uses the atomic write operation instructions provided by the CPU to atomically switch the system from one consistent state to another consistent state, and further supports lock-free query. Based on the volatile lock management mechanism, MPKV also introduces a concurrent write elimination mechanism to improve the efficiency of concurrency between update operations. When two conflicting update operations occur, the concurrent write elimination mechanism allows one of the operations to return directly without any persistent memory allocation and write. Experiments show that MPKV has better performance and multicore scalability than pmemkv. Specifically, in the 18-thread environment, the throughput of MPKV reaches 1.7 to 6.2 times of pmemkv.

Key words: persistent memory, multicore architecture, key-value store, concurrency control, crash consistency