Concurrent hash tables on multicore machines: Comparison, evaluation and implications

Concurrent hash table has been an area of active research in recent years, and a wide variety of fast and efficient concurrent hash tables (CHTs) have been proposed to exploit the advantages of modern parallel computer architectures such as today's mainstream multi-core systems. As one of the fundamental data structures widely used in software systems, existing works on CHTs focus on either algorithmic improvements, or hardware-oriented optimizations, or application-specific designs. However, there is a lack of a comprehensive and comparative study on different implementations. In this paper, we conduct an experimental study on the state-of-the-art, and our goal is to critically review existing CHTs from wider aspects and with more detailed analysis. Concretely, we have conducted extensive evaluations of five CHTs using a unified testing framework on four multi-core hardware platforms, and implemented our HTM-based concurrent hash table. A variety of metrics such as throughput scalability, latency, impact of memory hierarchy, thread pinning strategies, synchronization mechanisms, and memory consumption, are measured in order to obtain the deep insights about performance impediments and good design choices. With this study, we hope to identify potential issues and pinpoint promising directions for future research of CHTs.