GPH: An Efficient and Effective Perfect Hashing Scheme for GPU Architectures

Hash tables are widely used to support fast lookup operations for various applications on key-value stores and relational databases. In recent years, hash tables have been significantly improved by utilizing the high memory bandwidth and large parallelism degree offered by Graphics Processing Units (GPUs). However, there is still a lack of comprehensive analysis of the lookup performance on existing GPU-based hash tables. In this work, we develop a micro-benchmark and devise an effective and general performance analysis model, which enables uniform and accurate lookup performance evaluation of GPU-based hash tables. Moreover, we propose GPH, a novel GPU-based hash table, to improve lookup performance with the guidance of the benchmark results from the analysis model devised above. In particular, GPH employs the perfect hashing scheme that ensures exactly 1 bucket probe for every lookup operation. Besides, we optimize the bucket requests to global memory in GPH by devising vectorization and instruction-level parallelism techniques. We also introduce the insert kernel in GPH to support dynamic updates (e.g., processing insert operations) on GPU. Experimentally, GPH achieves over 8500 million operations per second (MOPS) for lookup operation processing in both synthetic and real-world workloads, which outperforms all evaluated GPU-based hash tables.