From: Jakub Kicinski Date: Thu, 30 Jul 2026 00:12:29 +0000 (-0700) Subject: Merge branch 'revert-tun-tap-vhost-net-apply-qdisc-backpressure-on-full-ptr_ring... X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7e107ab85cd40752a06e1788e10b0692fb021cbf;p=thirdparty%2Fkernel%2Fstable.git Merge branch 'revert-tun-tap-vhost-net-apply-qdisc-backpressure-on-full-ptr_ring-to-reduce-tx-drops' Simon Schippers says: ==================== Revert "tun/tap & vhost-net: apply qdisc backpressure on full ptr_ring to reduce TX drops" Commit 1d6e569b7d0c ("tun/tap & vhost-net: avoid ptr_ring tail-drop when a qdisc is present") did not show a relevant performance regression in my testing, but on Brett Sheffield's librecast testbed it causes a significant throughput drop in an IPv6 multicast testcase. The regression can be pinpointed to multiple iperf3 TCP threads sending: for 8 threads the throughput dropped from 13.5 Gbit/s to 9.13 Gbit/s. Therefore this series reverts the qdisc backpressure work. Making the backpressure opt-in via a new IFF_BACKPRESSURE flag was proposed in [1], but a new IFF_* flag needs more review scrutiny than is available at the moment, so a revert was requested instead. The opt-in will be resubmitted for net-next later. [1] Link: https://lore.kernel.org/netdev/20260709095511.168235-1-simon.schippers@tu-dortmund.de/ Reported-by: Brett Sheffield Closes: https://lore.kernel.org/netdev/akVnoOYQOrt8k-Gu@karahi.librecast.net/ ==================== Link: https://patch.msgid.link/20260728092240.250257-1-simon.schippers@tu-dortmund.de Signed-off-by: Jakub Kicinski --- 7e107ab85cd40752a06e1788e10b0692fb021cbf