Lorenzo Bianconi wrote:
> Update multi-buffer bit (mb) in xdp_buff to notify XDP/eBPF layer and
> XDP remote drivers if this is a "non-linear" XDP buffer. Access
> skb_shared_info only if xdp_buff mb is set in order to avoid possible
> cache-misses.
>
> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
[...]
> @@ -2320,8 +2325,12 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
> struct xdp_buff *xdp, u32 desc_status)
> {
> struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> - int i, num_frags = sinfo->nr_frags;
> struct sk_buff *skb;
> + u8 num_frags;
> + int i;
> +
> + if (unlikely(xdp_buff_is_mb(xdp)))
> + num_frags = sinfo->nr_frags;
Doesn't really need a respin IMO, but rather an observation. Its not
obvious to me the unlikely/likely pair here is wanted. Seems it could
be relatively common for some applications sending jumbo frames.
Maybe worth some experimenting in the future.
>
> skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
> if (!skb)
> @@ -2333,6 +2342,9 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
> skb_put(skb, xdp->data_end - xdp->data);
> skb->ip_summed = mvneta_rx_csum(pp, desc_status);
>
> + if (likely(!xdp_buff_is_mb(xdp)))
> + goto out;
> +
> for (i = 0; i < num_frags; i++) {
> skb_frag_t *frag = &sinfo->frags[i];
