FG-PFC: A Fine-Grained PFC Mechanism for Lossless RDMA

Abstract

Remote Direct Memory Access (RDMA) is widely deployed in data centers to improve the performance, efficiency, and reliability of data centers. Priority-based Flow Control (PFC) can ensure no packet loss as a necessary approach to achieve lossless RDMA. However, since PFC is a coarse-grained flow control mechanism based on port and priority, it can cause the head-of-line blocking problem and affect other flows, resulting in high latency. In this paper, we propose a fine-grained PFC mechanism (FG-PFC), which refines port and priority into flow granularity and further determines and pauses the flow most likely to cause congestion. The benefit is reducing the persistent high occupancy of the buffer and protecting the innocent flow. Simulations and experiments demonstrate that FG-PFC outperforms PFC in terms of flow completion time (FCT).