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Simon Schippers says: ==================== tun/tap & vhost-net: apply qdisc backpressure on full ptr_ring to reduce TX drops This patch series deals with tun/tap & vhost-net which drop incoming SKBs whenever their internal ptr_ring buffer is full. Instead, with this patch series, the associated netdev queue is stopped - but only when a qdisc is attached. If no qdisc is present the existing behavior is preserved. The XDP transmit path is not affected. This patch series touches tun/tap and vhost-net, as they share common logic and must be updated together. Modifying only one of them would break the other. By applying proper backpressure, this change allows the connected qdisc to operate correctly, as reported in [1], and significantly improves performance in real-world scenarios, as demonstrated in our paper [2]. For example, we observed a 36% TCP throughput improvement for an OpenVPN connection between Germany and the USA. Synthetic pktgen benchmarks indicate a slight regression, and packet loss is reduced to near zero. Pktgen benchmarks are provided per commit, with the final commit showing the overall performance. [1] Link: https://unix.stackexchange.com/questions/762935/traffic-shaping-ineffective-on-tun-device [2] Link: https://cni.etit.tu-dortmund.de/storages/cni-etit/r/Research/Publications/2025/Gebauer_2025_VTCFall/Gebauer_VTCFall2025_AuthorsVersion.pdf ==================== Link: https://patch.msgid.link/20260510151529.43895-1-simon.schippers@tu-dortmund.de Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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