On 30/10/2018 1:25 AM, Eric Dumazet wrote:
> This patch has two changes :
>
> 1) Use netdev_tx_sent_queue_more() for skbs with xmit_more
> This avoids mangling BQL status, since we only need to
> take care of it for the last skb of the batch.
>
> 2) doorbel only depends on xmit_more and netif_tx_queue_stopped()
>
> While not strictly necessary after 1), it is more consistent
> this way.
>
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Cc: Tariq Toukan <tar...@mellanox.com>
> ---
> drivers/net/ethernet/mellanox/mlx4/en_tx.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> index
> 1857ee0f0871d48285a6d3711f7c3e9a1e08a05f..3acce02ade6a115881ecd72e4710e332d3f380cb
> 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> @@ -1006,7 +1006,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct
> net_device *dev)
> ring->packets++;
> }
> ring->bytes += tx_info->nr_bytes;
> - netdev_tx_sent_queue(ring->tx_queue, tx_info->nr_bytes);
> AVG_PERF_COUNTER(priv->pstats.tx_pktsz_avg, skb->len);
>
> if (tx_info->inl)
> @@ -1044,7 +1043,14 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct
> net_device *dev)
> netif_tx_stop_queue(ring->tx_queue);
> ring->queue_stopped++;
> }
> - send_doorbell = !skb->xmit_more || netif_xmit_stopped(ring->tx_queue);
> +
> + if (skb->xmit_more) {
> + netdev_tx_sent_queue_more(ring->tx_queue, tx_info->nr_bytes);
> + send_doorbell = netif_tx_queue_stopped(ring->tx_queue);
> + } else {
> + netdev_tx_sent_queue(ring->tx_queue, tx_info->nr_bytes);
> + send_doorbell = true;
> + }
>
> real_size = (real_size / 16) & 0x3f;
>
>
The drivers' code template would be nicer if we unify the two functions
netdev_tx_sent_queue/netdev_tx_sent_queue_more to a single one with a
parameter.
Currently, all drivers that would want to benefit from this optimization
will have to repeat these if/else blocks.
Regards,
Tariq
