Processor Assisted Worklist Scheduling for FPGA Accelerated Graph Processing on a Shared-Memory Platform

FPGA-based processing has gained much attention for accelerating graph analytics because of the demand in performance and energy efficiency. However, while priority scheduling has been shown to be an effective optimization for improving performance for worklist-based graph computations, it is rarely used in accelerator designs due to its implementation complexity and memory-access overhead. In this paper, we present a heterogeneous processing approach for priority scheduling on a shared-memory CPU-FPGA platform. By exploiting the closely-coupled integration of the host processor and the FPGA accelerator, our system dynamically offloads the task of scheduling to a software scheduler on the processor for its programmability, high-capacity cache and low memory latency, while the FPGA graph processing accelerator enjoys the scheduling benefit and delivers higher performance at excellent energy efficiency. To understand the effectiveness of our solution, we compared it with FPGA-only solutions for two scheduling schemes: the well-known Dijkstra scheduling for Single Source Shortest Path and a new scheduling optimization we developed for improving the data locality of Breadth First Search. Whereas the FPGA-only solution requires an impractical amount of on-chip storage to implement a priority queue, the proposed processor-assisted scheduling that moves the task of scheduling to the processor consumes a negligible load on the processor and retains most of the performance benefit from priority scheduling.