F-PFC: Enabling Fine-Grained PFC in Lossless Data Center Networks

Data centers rely on Priority-based Flow Control (PFC) to achieve lossless data transmission in Ethernet networks. To avoid buffer overflow, PFC pauses flows in a coarse-grained manner, which brings potential problems, e.g., Head-of-Line (HoL) blocking, and PFC deadlock. Although the state-of-the-art approach BFC with per-flow backpressure tackles some of the limitations of PFC, it faces implementation challenges due to the need for a large number of queues. In this paper, we present F-PFC, a fine-grained flow control scheme that only leverages a small amount of queues to address the limitations of PFC. Specifically, F-PFC first designs a fine-grained flow backpressure scheme to adjust the intensity of flow control adaptively. With different levels of flow backpressure, F-PFC ensures high throughput and low latency simultaneously. Then, F-PFC presents an accurate flow identification scheme to locate flows that really contribute to congestion. Finally, F-PFC presents a dynamic queue assignment and scheduling scheme to isolate congestion flows with limited queues. We theoretically analyze the performance of F-PFC and present the implementation of F-PFC. Extensive testbed experiments and large-scale simulations verify the performance of F-PFC. The experimental results show that F-PFC reduces tail latency by at least 33% and queue occupancy by 46% compared with state-of-the-art approaches.