On Wed, 19 Aug 2020 15:13:48 +0200
Lorenzo Bianconi <lore...@kernel.org> 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
>
> Signed-off-by: Lorenzo Bianconi <lore...@kernel.org>
> ---
> drivers/net/ethernet/marvell/mvneta.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c
> b/drivers/net/ethernet/marvell/mvneta.c
> index 832bbb8b05c8..36a3defa63fa 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2170,11 +2170,14 @@ mvneta_run_xdp(struct mvneta_port *pp, struct
> mvneta_rx_queue *rxq,
> struct bpf_prog *prog, struct xdp_buff *xdp,
> u32 frame_sz, struct mvneta_stats *stats)
> {
> + struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> unsigned int len, data_len, sync;
> u32 ret, act;
>
> len = xdp->data_end - xdp->data_hard_start - pp->rx_offset_correction;
> data_len = xdp->data_end - xdp->data;
> +
> + xdp->mb = !!sinfo->nr_frags;
> act = bpf_prog_run_xdp(prog, xdp);
Reading the memory sinfo->nr_frags could be a performance issue for our
baseline case of no-multi-buffer. As you are reading a cache-line that
you don't need to (and driver have not touch yet).
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
