[PATCH net-next v7 9/9] tun/tap & vhost-net: avoid ptr_ring tail-drop when qdisc is present

On 1/12/26 12:19, Michael S. Tsirkin wrote:

On Mon, Jan 12, 2026 at 12:17:12PM +0100, Simon Schippers wrote:

quoted

On 1/12/26 05:33, Michael S. Tsirkin wrote:

quoted

On Fri, Jan 09, 2026 at 11:14:54AM +0100, Simon Schippers wrote:

quoted

Am I not allowed to stop the queue and then return NETDEV_TX_BUSY?

We jump through a lot of hoops in virtio_net to avoid using
NETDEV_TX_BUSY because that bypasses all the net/ cleverness.
Given your patches aim to improve precisely ring full,
I would say stopping proactively before NETDEV_TX_BUSY
should be a priority.

I already proactively stop here with the approach you proposed in
the v6.
Or am I missing something (apart from the xdp path)?

Yes, I am just answering the general question you posed.

Ah okay.

quoted

And yes I also dislike returning NETDEV_TX_BUSY but I do not see how
this can be prevented with lltx enabled.

Preventing NETDEV_TX_BUSY 100% of the time is not required. It's there
to handle races.

Great to know. Thanks