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/[email protected]/ Reported-by: Brett Sheffield <[email protected]> Closes: https://lore.kernel.org/netdev/[email protected]/ Simon Schippers (4): Revert "tun/tap & vhost-net: avoid ptr_ring tail-drop when a qdisc is present" Revert "ptr_ring: move free-space check into separate helper" Revert "vhost-net: wake queue of tun/tap after ptr_ring consume" Revert "tun/tap: add ptr_ring consume helper with netdev queue wakeup" drivers/net/tun.c | 109 +++------------------------------------ drivers/vhost/net.c | 21 +++----- include/linux/if_tun.h | 3 -- include/linux/ptr_ring.h | 20 +------ 4 files changed, 14 insertions(+), 139 deletions(-) base-commit: b14361aca6350ff7907b0e9903c7b94dc7d5d4a0 -- 2.43.0
