GNNPipe: Accelerating Distributed Full-Graph GNN Training with Pipelined Model Parallelism

Current distributed full-graph GNN training methods adopt a variant of data parallelism, namely graph parallelism, in which the whole graph is divided into multiple partitions (subgraphs) and each GPU processes one of them. This incurs high communication overhead because of the inter-partition message passing at each layer. To this end, we proposed a new training method named GNNPipe that adopts model parallelism instead, which has a lower worst-case asymptotic communication complexity than graph parallelism. To ensure high GPU utilization, we proposed to combine model parallelism with a chunk-based pipelined training method, in which each GPU processes a different chunk of graph data at different layers concurrently. We further proposed hybrid parallelism that combines model and graph parallelism when the model-level parallelism is insufficient. We also introduced several tricks to ensure convergence speed and model accuracies to accommodate embedding staleness introduced by pipelining. Extensive experiments show that our method reduces the per-epoch training time by up to 2.45x (on average 2.03x) and reduces the communication volume and overhead by up to 22.51x and 27.21x (on average 10.27x and 14.96x), respectively, while achieving a comparable level of model accuracy and convergence speed compared to graph parallelism.