Yangshen Deng

Improving the performance of GPU query processing is a well-studied problem in database community. However, its performance is still unsatisfactory due to the low utilization of GPU memory bandwidth. In the literature, employing software prefetching techniques to improve the bandwidth utilization is a common practice in CPU database as it overlaps computation cost and memory access latency. However, it was ignored by GPU database even though the software prefetching ability has been provided by modern GPU architecture (i.e., from NVIDIA Ampere).In order to investigate the effectiveness of software prefetching techniques on GPU query processing, we implement four software prefetching algorithms on GPU, i.e., Group Prefetch (GP), Software-Pipelined Prefetch (SPP), Asynchronous Memory Access Chaining (AMAC) and Interleaved Multi-Vectorizing (IMV) in the work. We then adapt them on hash join probe and BTree search tasks with a suite of optimizations. Last, we conduct comprehensive experiments and evaluate the performance of them. The results confirm the superiority of software prefetching techniques on GPU query processing. Specifically, they can achieve up to 1.19X speedup on hash join probe and 1.31X speedup on BTree search when compared with the implementations without software prefetching.

Merkle Patricia Trie (MPT) is a type of trie structure that offers efficient lookup and insert operators for immutable data systems that require multi-version access and tamper-evident controls, such as blockchains and verifiable databases. The performance of these systems is critically dependent on the throughput of the underlying index structure MPT. In this paper, we present a novel approach to accelerate MPT by leveraging the massive parallelism of GPU. However, achieving it is challenging as (i) lock-free data structures are difficult to implement and (ii) traditional fine-grained locking does not scale on GPU. To address them, we first analyze the technical challenges of accelerating MPT via GPU, including node splitting conflicts and hash computing conflicts caused by parallel insert operations. We then propose a lock-free algorithm PhaseNU and a lock-based algorithm LockNU on GPU to resolve the node splitting conflict. We also devise a decision model for users to choose the proper one for different workloads. We next propose a GPU-based hash compute algorithm PhaseHC to avoid hash computing conflicts. Last, we demonstrate the effectiveness of our proposed techniques by: (i) integrating them into both the real-world blockchain system Geth and verifiable database LedgerDB, and demonstrating its superiority with corresponding workloads; and (ii) conducting extensive experimental studies on two real-world datasets and one synthetic dataset. Our proposed solutions significantly outperform the deployed MPT solution in Geth in all datasets.

As a popular distributed data warehouse system, Apache Hive has been widely used for big data analytics in many organizations. Meanwhile, exploiting the massive parallelism of GPU to accelerate online analytical processing (OLAP) has been extensively explored in the database community. In this paper, we present GHive, which enhances CPU-based Hive via CPU-GPU heterogeneous computing. GHive is designed for the business intelligence applications and provides the same API as Hive for compatibility. To run SQL queries jointly on both CPU and GPU, GHive comes with three key techniques: (i) a novel data model gTable, which is column-based and enables efficient data movement between CPU memory and GPU memory; (ii) a GPU-based operator library Panda, which provides a complete set of SQL operators with extensively optimized GPU implementations; (iii) a hardware-aware MapReduce job placement scheme, which puts jobs judiciously on either GPU or CPU via a cost-based approach. In the experiments, we observe that GHive outperforms Hive in both query processing speed and operating expense on the Star Schema Benchmark (SSB).

As a distributed, fault-tolerant data warehouse system for large-scale data analytics, Apache Hive has been used for various applications in many organizations (e.g., Facebook, Amazon, and Huawei). Exploiting the large degrees of parallelism of GPU to improve the performance of online analytical processing (OLAP) in database system is a common practice in the industry. Meanwhile, it is a common practice to exploit the large degrees of parallelism of GPU to improve the performance of online analytical processing (OLAP) in database systems. This demo presents GHive, which enables Apache Hive to accelerate OLAP queries by jointly utilizing CPU and GPU in intelligent and efficient ways. The takeaways for SIGMOD attendees include: (1) the superior performance of GHive compared with vanilla Hive that only uses CPU; (2) intuitive visualizations of execution statistics for Hive and GHive to understand where the acceleration of GHive comes from; (3) detailed profiling of the time taken by each operator on CPU and GPU to show the advantages of GPU execution.