Re: [PATCH net-next 2/2] virtio-net: simplify XDP handling in small buffer

From: Jesper Dangaard Brouer
Date: Thu Mar 01 2018 - 04:16:18 EST


On Thu, 1 Mar 2018 16:49:24 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:

> > 2. This can easily cause out-of-order packets.
>
> I may miss something, but it looks to me packets were still delivered
> in order? Or you mean the packets that was dropped by cpumap?

No. Packets can now travel two code paths to the egress device. (1) XDP
native via ndp_xdp_xmit via direct delivery into a lockfree/dedicated
TX queue, (2) via normal network stack which can involve being queue in
a qdisc. Do you see the possibility of the reorder now?

--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer