Subject: Re: [PATCH v4 net-next 5/5] net: mlx5: add xdp tx return bulking support

From: Jesper Dangaard Brouer <[email-masked]>
Date: Tue, 10 Nov 2020 11:48:58 +0100

On Fri,  6 Nov 2020 19:19:11 +0100
Lorenzo Bianconi <[email-masked]> wrote:

> Convert mlx5 driver to xdp_return_frame_bulk APIs.
> 
> XDP_REDIRECT (upstream codepath): 8.5Mpps
> XDP_REDIRECT (upstream codepath + bulking APIs): 10.1Mpps
> 
> Signed-off-by: Lorenzo Bianconi <[email-masked]>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

This patch is not 100% correct.  The bulking need to happen at another
level.  I have already fixed this up in the patches I'm currently
benchmarking with.  (Lorenzo is informed and aware)

Too many details, but all avail in[1].
 [1] https://github.com/xdp-project/xdp-project/blob/master/areas/mem/xdp_bulk_return01.org

> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
> index ae90d533a350..5fdfbf390d5c 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
> @@ -369,8 +369,10 @@ static void mlx5e_free_xdpsq_desc(struct mlx5e_xdpsq *sq,
>  				  bool recycle)
>  {
>  	struct mlx5e_xdp_info_fifo *xdpi_fifo = &sq->db.xdpi_fifo;
> +	struct xdp_frame_bulk bq;
>  	u16 i;
>  
> +	bq.xa = NULL;
>  	for (i = 0; i < wi->num_pkts; i++) {
>  		struct mlx5e_xdp_info xdpi = mlx5e_xdpi_fifo_pop(xdpi_fifo);
>  
> @@ -379,7 +381,7 @@ static void mlx5e_free_xdpsq_desc(struct mlx5e_xdpsq *sq,
>  			/* XDP_TX from the XSK RQ and XDP_REDIRECT */
>  			dma_unmap_single(sq->pdev, xdpi.frame.dma_addr,
>  					 xdpi.frame.xdpf->len, DMA_TO_DEVICE);
> -			xdp_return_frame(xdpi.frame.xdpf);
> +			xdp_return_frame_bulk(xdpi.frame.xdpf, &bq);
>  			break;
>  		case MLX5E_XDP_XMIT_MODE_PAGE:
>  			/* XDP_TX from the regular RQ */
> @@ -393,6 +395,7 @@ static void mlx5e_free_xdpsq_desc(struct mlx5e_xdpsq *sq,
>  			WARN_ON_ONCE(true);
>  		}
>  	}
> +	xdp_flush_frame_bulk(&bq);
>  }
>  
>  bool mlx5e_poll_xdpsq_cq(struct mlx5e_cq *cq)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer