[dpdk-dev] [PATCH] net/virtio: fix wrong TX pkt length stats

[Maxime Coquelin]

Hi Zhiyong,

On 10/11/2017 06:39 AM, Zhiyong Yang wrote:
> In the function virtqueue_enqueue_xmit(), when can_push == 1 is true,
> vtnet_hdr_size is added to pkt_len by calling rte_pktmbuf_prepend.
> So, virtio header len should be subtracted before calling stats
> function.
> 
> Fixes: 58169a9c8153 ("net/virtio: support Tx checksum offload")
> 
> Signed-off-by: Zhiyong Yang <zhiyong.yang at intel.com>
> ---
>   drivers/net/virtio/virtio_rxtx.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 609b4138a..bf14f9a99 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -1079,6 +1079,12 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
>   		/* Enqueue Packet buffers */
>   		virtqueue_enqueue_xmit(txvq, txm, slots, use_indirect, can_push);
>   
> +		/* In function virtqueue_enqueue_xmit(), when can_push == 1
> +		 * is true, vtnet_hdr_size is added to pkt_len of mbuf. So, it
> +		 * should be subtracted before calling stats function.
> +		 */
> +		if (can_push == 1)
> +			txm->pkt_len -= txvq->vq->hw->vtnet_hdr_size;
>   		txvq->stats.bytes += txm->pkt_len;

I acknowledge the problem, but I don't like modifying pkt_len.
This is not the case currently, but in case we want to do something
with the mbuf later in virtio_xmit_cleanup(), it could be good to have
the real length there.

What about:

if (can_push == 1)
     txvq->stats.bytes += txm->pkt_len - txvq->vq->hw->vtnet_hdr_size;
else
     txvq->stats.bytes += txm->pkt_len;

Thanks,
Maxime

>   		virtio_update_packet_stats(&txvq->stats, txm);
>   	}
>