Re: [PATCH RFC net-next 4/4] veth: use generic skb XDP handling

["Björn Töpel" <bjorn@kernel.org>]

Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes:

> veth currently runs XDP for skb-backed packets by constructing an
> xdp_buff and then, for XDP_TX and XDP_REDIRECT, converting that
> skb-backed xdp_buff into an xdp_frame. The backing memory is still
> skb-owned, so veth has to pin the skb data and frags manually before
> consuming the skb.
>
> Use the generic skb XDP helper for skb-backed packets instead. This
> keeps skb-backed packets on the skb generic XDP path: XDP_REDIRECT uses
> xdp_do_generic_redirect() and XDP_TX uses generic_xdp_tx(). Packets that
> already arrive as xdp_frames keep using the existing veth xdp_frame path.
>
> veth still provides its own page_pool and xdp_rxq_info through struct
> xdp_generic_ctx. It also keeps using struct veth_xdp_buff storage so
> metadata kfuncs that need the skb continue to work after a possible skb
> COW.


Hmm, so now if veth with native XDP redirects to a native XDP NIC, we'll
end up in the generic path? We'll loose some bulking capabilities as
well, but maybe that's OK.

I guess what I'm saying is that some performance numbers would help
here! ;-)

(I think it might be some accounting bug as well, but I need to re-read
it!)


Björn