Subject: Re: [PATCH bpf-next 2/4] xsk: allow AF_XDP sockets to receive packets directly from a queue

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Tue, 08 Oct 2019 08:58:16 +0200

Sridhar Samudrala <[email-masked]> writes:

>  int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
>  		    struct bpf_prog *xdp_prog)
>  {
>  	struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
>  	struct bpf_map *map = READ_ONCE(ri->map);
> +	struct xdp_sock *xsk;
> +
> +	xsk = xdp_get_direct_xsk(ri);
> +	if (xsk)
> +		return xsk_rcv(xsk, xdp);

This is a new branch and a read barrier in the XDP_REDIRECT fast path.
What's the performance impact of that for non-XSK redirect?

-Toke