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>
> ---
> drivers/net/ethernet/marvell/mvneta.c | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 5d1007e1b5c9..9f4858e35566 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2037,9 +2037,14 @@ mvneta_xdp_put_buff(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
> {
> int i;
>
> + if (likely(!xdp_buff_is_mb(xdp)))
> + goto out;
> +
Wouldn't nr_frags = 0 in the !xdp_buff_is_mb case? Is the
xdp_buff_is_mb check with goto really required?
> for (i = 0; i < sinfo->nr_frags; i++)
> page_pool_put_full_page(rxq->page_pool,
> skb_frag_page(&sinfo->frags[i]), true);
> +
> +out:
> page_pool_put_page(rxq->page_pool, virt_to_head_page(xdp->data),
> sync_len, true);
> }
> @@ -2241,7 +2246,6 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
> int data_len = -MVNETA_MH_SIZE, len;
> struct net_device *dev = pp->dev;
> enum dma_data_direction dma_dir;
> - struct skb_shared_info *sinfo;
>
> if (*size > MVNETA_MAX_RX_BUF_SIZE) {
> len = MVNETA_MAX_RX_BUF_SIZE;
> @@ -2261,11 +2265,9 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
>
> /* Prefetch header */
> prefetch(data);
> + xdp_buff_clear_mb(xdp);
> xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
> data_len, false);
> -
> - sinfo = xdp_get_shared_info_from_buff(xdp);
> - sinfo->nr_frags = 0;
> }
>
> static void
> @@ -2299,6 +2301,9 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
> skb_frag_off_set(frag, pp->rx_offset_correction);
> skb_frag_size_set(frag, data_len);
> __skb_frag_set_page(frag, page);
> +
> + if (!xdp_buff_is_mb(xdp))
> + xdp_buff_set_mb(xdp);
> } else {
> page_pool_put_full_page(rxq->page_pool, page, true);
> }
> @@ -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;
>
> 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;
> +
Not that I care much, but couldn't you just init num_frags = 0 and
avoid the goto?
Anyways its not my driver so no need to change it if you like it better
the way it is. Mostly just checking my understanding.
> for (i = 0; i < num_frags; i++) {
> skb_frag_t *frag = &sinfo->frags[i];
>
> @@ -2341,6 +2353,7 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
> skb_frag_size(frag), PAGE_SIZE);
> }
>
> +out:
> return skb;
> }
>
> --
> 2.31.1
>
