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SubjectRe: [RFC PATCH net-next V2 6/6] virtio-net: support XDP rx handler
On Mon, 13 Aug 2018 11:17:30 +0800
Jason Wang <jasowang@redhat.com> wrote:

> This patch tries to add the support of XDP rx handler to
> virtio-net. This is straight-forward, just call xdp_do_pass() and
> behave depends on its return value.
>
> Test was done by using XDP_DROP (xdp1) for macvlan on top of
> virtio-net. PPS of SKB mode was ~1.2Mpps while PPS of native XDP mode
> was ~2.2Mpps. About 83% improvement was measured.

I'm not convinced...

Why are you not using XDP_REDIRECT, which is already implemented in
receive_mergeable (which you modify below).

The macvlan driver just need to implement ndo_xdp_xmit(), and then you
can redirect (with XDP prog from physical driver into the guest). It
should be much faster...


> Notes: for RFC, only mergeable buffer case was implemented.
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/net/virtio_net.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 62311dd..1e22ad9 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -777,6 +777,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> rcu_read_lock();
> xdp_prog = rcu_dereference(rq->xdp_prog);
> if (xdp_prog) {
> + rx_xdp_handler_result_t ret;
> struct xdp_frame *xdpf;
> struct page *xdp_page;
> struct xdp_buff xdp;
> @@ -825,6 +826,15 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>
> switch (act) {
> case XDP_PASS:
> + ret = xdp_do_pass(&xdp);
> + if (ret == RX_XDP_HANDLER_DROP)
> + goto drop;
> + if (ret != RX_XDP_HANDLER_FALLBACK) {
> + if (unlikely(xdp_page != page))
> + put_page(page);
> + rcu_read_unlock();
> + goto xdp_xmit;
> + }
> /* recalculate offset to account for any header
> * adjustments. Note other cases do not build an
> * skb and avoid using offset
> @@ -881,6 +891,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
> case XDP_ABORTED:
> trace_xdp_exception(vi->dev, xdp_prog, act);
> /* fall through */
> +drop:
> case XDP_DROP:
> if (unlikely(xdp_page != page))
> __free_pages(xdp_page, 0);



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

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