netdev - Re: [net-next PATCH V1 2/3] mlx4: use napi_alloc

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Date:	Mon, 9 May 2016 09:47:08 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Saeed Mahameed <saeedm@...lanox.com>,
	Or Gerlitz <gerlitz.or@...il.com>,
	Eugenia Emantayev <eugenia@...lanox.com>
Subject: Re: [net-next PATCH V1 2/3] mlx4: use napi_alloc_skb API to get SKB
 bulk allocations

On Mon, May 9, 2016 at 6:44 AM, Jesper Dangaard Brouer
<brouer@...hat.com> wrote:
> Activate the bulk alloc API, simply by changing mlx4 from using
> netdev_alloc_skb() to using napi_alloc_skb().

This patch is just enabling the napi_alloc_skb call.  You don't need
to call out that it is enabling bulk allocations.  This patch could
stand on its own without needing to make reference to the bulk
allocation API because there is enough of a gain from napi_alloc_skb
replacing netdev_alloc_skb.

> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 8ef6875b6cf9..84fd6db5a176 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -577,14 +577,15 @@ fail:
>  static struct sk_buff *mlx4_en_rx_skb(struct mlx4_en_priv *priv,
>                                       struct mlx4_en_rx_desc *rx_desc,
>                                       struct mlx4_en_rx_alloc *frags,
> -                                     unsigned int length)
> +                                     unsigned int length,
> +                                     struct napi_struct *napi)

Instead of passing the NAPI structure you could just pass the
mlx4_en_cq pointer to be used by the NAPI alloc function.  In addition
you might try adding the new parameter before length since that way
the pointers are in one block followed by integers in a tapering
length order.

>  {
>         struct sk_buff *skb;
>         void *va;
>         int used_frags;
>         dma_addr_t dma;
>
> -       skb = netdev_alloc_skb(priv->dev, SMALL_PACKET_SIZE + NET_IP_ALIGN);
> +       skb = napi_alloc_skb(napi, SMALL_PACKET_SIZE + NET_IP_ALIGN);

The NET_IP_ALIGN is redundant as napi_alloc_skb already takes are of
adding that and NET_SKB_PAD.

>         if (!skb) {
>                 en_dbg(RX_ERR, priv, "Failed allocating skb\n");
>                 return NULL;
> @@ -932,7 +933,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
>                 }
>
>                 /* GRO not possible, complete processing here */
> -               skb = mlx4_en_rx_skb(priv, rx_desc, frags, length);
> +               skb = mlx4_en_rx_skb(priv, rx_desc, frags, length, &cq->napi);
>                 if (!skb) {
>                         ring->dropped++;
>                         goto next;
>