On Sat, Dec 19, 2020 at 4:56 PM Shay Agroskin <shayagr@xxxxxxxxxx> wrote:
>
>
> Lorenzo Bianconi <lorenzo@xxxxxxxxxx> writes:
>
> > Introduce the capability to map non-linear xdp buffer running
> > mvneta_xdp_submit_frame() for XDP_TX and XDP_REDIRECT
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> > ---
> > drivers/net/ethernet/marvell/mvneta.c | 94
> > ++++++++++++++++-----------
> > 1 file changed, 56 insertions(+), 38 deletions(-)
> [...]
> > if (napi && buf->type ==
> > MVNETA_TYPE_XDP_TX)
> > xdp_return_frame_rx_napi(buf->xdpf);
> > else
> > @@ -2054,45 +2054,64 @@ mvneta_xdp_put_buff(struct mvneta_port
> > *pp, struct mvneta_rx_queue *rxq,
> >
> > static int
> > mvneta_xdp_submit_frame(struct mvneta_port *pp, struct
> > mvneta_tx_queue *txq,
> > - struct xdp_frame *xdpf, bool dma_map)
> > + struct xdp_frame *xdpf, int *nxmit_byte,
> > bool dma_map)
> > {
> > - struct mvneta_tx_desc *tx_desc;
> > - struct mvneta_tx_buf *buf;
> > - dma_addr_t dma_addr;
> > + struct xdp_shared_info *xdp_sinfo =
> > xdp_get_shared_info_from_frame(xdpf);
> > + int i, num_frames = xdpf->mb ? xdp_sinfo->nr_frags + 1 :
> > 1;
> > + struct mvneta_tx_desc *tx_desc = NULL;
> > + struct page *page;
> >
> > - if (txq->count >= txq->tx_stop_threshold)
> > + if (txq->count + num_frames >= txq->size)
> > return MVNETA_XDP_DROPPED;
> >
> > - tx_desc = mvneta_txq_next_desc_get(txq);
> > + for (i = 0; i < num_frames; i++) {
> > + struct mvneta_tx_buf *buf =
> > &txq->buf[txq->txq_put_index];
> > + skb_frag_t *frag = i ? &xdp_sinfo->frags[i - 1] :
> > NULL;
> > + int len = frag ? xdp_get_frag_size(frag) :
> > xdpf->len;
>
> nit, from branch prediction point of view, maybe it would be
> better to write
> int len = i ? xdp_get_frag_size(frag) : xdpf->len;
>
ack, I will fix it in v6.
Regards,
Lorenzo
> since the value of i is checked one line above
> Disclaimer: I'm far from a compiler expert, and don't know whether
> the compiler would know to group these two assignments together
> into a single branch prediction decision, but it feels like using
> 'i' would make this decision easier for it.
>
> Thanks,
> Shay
>
> [...]
>
