netdev - Re: [net-next PATCH V2 2/3] mlx4: use napi_consume

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Date:	Thu, 10 Mar 2016 16:59:08 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Cc:	eugenia@...lanox.com, Alexander Duyck <alexander.duyck@...il.com>,
	alexei.starovoitov@...il.com, saeedm@...lanox.com,
	gerlitz.or@...il.com
Subject: Re: [net-next PATCH V2 2/3] mlx4: use napi_consume_skb API to get
 bulk free operations

Hello.

On 3/10/2016 3:15 PM, Jesper Dangaard Brouer wrote:

> Bulk free of SKBs happen transparently by the API call napi_consume_skb().
> The napi budget parameter is usually needed by napi_consume_skb()
> to detect if called from netpoll.  In this patch it have an extra meaning.

    It has.

> For mlx4 driver, the mlx4_en_stop_port() call is done outside
> NAPI/softirq context, and cleanup the entire TX ring via
> mlx4_en_free_tx_buf().  The code mlx4_en_free_tx_desc() for
> freeing SKBs are shared with NAPI calls.
>
> To handle this shared use the zero budget indication is reused,
> and handled appropiately in napi_consume_skb(). To reflect this,

    Appropriately.

> variable is called napi_mode for the function call that needed
> this distinction.
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> ---
>   drivers/net/ethernet/mellanox/mlx4/en_tx.c |   16 ++++++++++------
>   1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> index e0946ab22010..1b41feafce9e 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
[...]
> @@ -371,7 +373,9 @@ int mlx4_en_free_tx_buf(struct net_device *dev, struct mlx4_en_tx_ring *ring)
>   	while (ring->cons != ring->prod) {
>   		ring->last_nr_txbb = mlx4_en_free_tx_desc(priv, ring,
>   						ring->cons & ring->size_mask,
> -						!!(ring->cons & ring->size), 0);
> +						!!(ring->cons & ring->size), 0,
> +						0 /* none-NAPI caller */

    Non-NAPI, perhaps?

[...]

MBR, Sergei