Re: [PATCH v5 bpf-next 06/14] net: mvneta: add multi buffer support to XDP_TX
From: Shay Agroskin <hidden>
Date: 2020-12-19 15:57:50
Also in:
bpf
Lorenzo Bianconi [off-list ref] 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@kernel.org> --- drivers/net/ethernet/marvell/mvneta.c | 94 ++++++++++++++++----------- 1 file changed, 56 insertions(+), 38 deletions(-)
[...]
quoted hunk ↗ jump to hunk
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;
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
[...]