> On Wed, 19 Aug 2020 15:13:48 +0200
> Lorenzo Bianconi <lorenzo@xxxxxxxxxx> 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 <lorenzo@xxxxxxxxxx>
> > ---
> > 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).
ack, I will rework it in v2 to remove this access.
Regards,
Lorenzo
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
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