Excavating the Potential of GPU for Accelerating Graph Traversal

Graph traversal is an essential procedure for a growing amount of applications today. This type of algorithms typically iterate input graph datasets until convergence and the logic of each iteration is quite simple. GPUs are used extensively as graph traversal accelerators due to the capability of massive parallelism and high-bandwidth memory access. However, existing methods are inefficient in two ways. First, streaming multiprocessors (SMs) are still underutilized due to the unbalanced load allocation and uncoalesced memory access. Second, they use space-inefficient data structures or need auxiliary data to assist traversal. It is undesirable, considering the limited GPU memory capacity. Moreover, existing designs commonly focus on optimizing kernel execution time. Data-transfer time is also notable in the whole procedure. Thus, space-efficient data structure and data-transfer policy should be concerned. In this paper, we propose EtaGraph, a novel GPU graph traversal framework optimized for GPU memory system and execution parallelism. EtaGraph has several features: 1). It uses a frontier-like kernel execution model, featuring a lightweight graph transformation procedure, named Unified Degree Cut, allowing GPU threads to process skewed graph efficiently without modification of raw data or introducing extra space overhead; 2). It uses on-demand data-transfer to overlap computation so that it optimizes the total time of data-transfer and execution; 3). It adopts an explicit utilization of Shared Memory to enhance memory coalescing and to improve effective memory bandwidth. Evaluation of EtaGraph shows significant and consistent speedups over the state-of-the-art GPU-based graph processing frameworks on both real-world and synthetic graphs.