Improving megaflow cache performance in Open vSwitch with branch prediction#

Speakers: Emil Stahl, KTH Royal Institute of Technology; Q&A portion hosted by Eelco Chaudron, Red Hat (from abstract only)

Why: An academic outsider's angle on a practitioner problem — the PM wouldn't search for this, and it may preview where datapath caching goes next.

What: The argument that the slow path (datapath ↔ control plane interaction on megaflow-cache misses) is poised to become the bottleneck in high-throughput networks, and that upcalls can be reduced by predicting imminent traffic — using coflows to anticipate flows before they miss the cache.

How: Benchmarks on an OVN-simulated single-node OCP cluster, with XDP timestamping packets at ingress and egress, driven by synthetic coflow traces with varying flow-size distributions; results analyze how prediction accuracy of varying proportions of future flows affects OVS latency.

Where applicable: Single-node simulation with synthetic traces — research-stage, not production guidance. The idea of predictive cache warming in a vSwitch is the novel hook.