On Wed, Apr 13, 2016 at 11:04:45AM +0200, Paolo Abeni wrote: > This patch series try to remove the need for any lock in the tun device > xmit path, significantly improving the forwarding performance when multiple > processes are accessing the tun device (i.e. in a nic->bridge->tun->vm > scenario). > > The lockless xmit is obtained explicitly setting the NETIF_F_LLTX feature bit > and removing the default qdisc. > > Unlikely most virtual devices, the tun driver has featured a default qdisc > for a long period, but it already lost such feature in linux 4.3.
Thanks - I think it's a good idea to reduce the lock contention there. But I think it's unfortunate that it requires bypassing the qdisc completely: this means that anyone trying to do traffic shaping will get back the contention. Can we solve the lock contention for qdisc? E.g. add a small lockless queue in front of it, whoever has the qdisc lock would be responsible for moving things from there to qdisc proper. Thoughts? Is there a chance this might work reasonably well? > Paolo Abeni (2): > tun: don't require serialization lock on tx > tun: don't set a default qdisc > > drivers/net/tun.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > -- > 1.8.3.1
