Holm: A DPU-Based Robust Host-Side Latency Monitoring with Low-Overhead and Selective Full-Coverage

Host-side packet processing latency occupies a significant proportion of the total end-to-end latency of TCP flows in DCNs. The monitoring of host-side latency is critical to achieve DCN performance diagnosis, troubleshooting, and service-level objectives. Existing solutions normally incur significant CPU consumption or lose full-coverage due to sampling, and are susceptible to host-side anomalies. In this paper, we propose a robust method termed as Holm to achieve host-side latency monitoring without host CPU consumption by offloading monitoring logic to DPU, and achieve monitoring coverage and resource balancing through differentially treating best-effort and latency-sensitive TCP flows. Holm first identifies best-effort and latency-sensitive TCP flows in DPU, and performs corresponding selective and full-coverage monitoring. A mathematical model is then established for evaluating the overall latency state of latency-sensitive TCP flows, and if abnormal increases are detected, foreboding the threat of packet overflow, a corresponding number of congestion notifications will be delivered to best-effort TCP flow senders for reducing host-side anomaly impacts. Holm is evaluated by our prototype implementation on NVIDIA BlueField-3 DPU. The experimental results indicate that compared to representative methods, it eliminates host CPU consumption with low-overhead and achieves robustness by improving coverage by up to 2.07× even under serious host-side congestion.