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AF_XDP copy mode needs more love#

Netdev 0x1A (Rome, 13-16 July 2026) digest Program Adjacent pick Rome · 13–16 July 2026

Abstract Slides Recording

Jason Xing

Play the recording: AF_XDP copy mode needs more love

Why: Zero-copy AF_XDP only works on a handful of drivers (ice, bnxt, mlx5) — for VMs on virtio-net, containers on veth, and the long tail of NICs, copy mode is the datapath, and it has been under-optimized.

What: Correctness fixes already merged (multi-buffer TX buffer leaks, continuation descriptor handling, a metadata TOCTOU) plus in-flight optimizations totalling close to 2x TX throughput.

How: No single fix — cycle-level perf analysis, lock-contention tracing, cache-line bouncing detection and structure layout heat-mapping applied across the copy-mode TX path. (From abstract only.)

Where applicable: Directly relevant to container and VM datapaths, which is where the copy path actually lives.