netdev - Re: [PATCH net 1/2] net: bcmgenet: fix dev->stats.tx

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Date:	Wed, 23 Mar 2016 14:23:57 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Petri Gynther <pgynther@...gle.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, f.fainelli@...il.com,
	jaedon.shin@...il.com, edumazet@...gle.com
Subject: Re: [PATCH net 1/2] net: bcmgenet: fix dev->stats.tx_bytes
 accounting

On Wed, 2016-03-23 at 13:01 -0700, Petri Gynther wrote:
> 1. Add bytes_compl local variable to collect transmitted bytes
>    - dev->stats updates can then be moved outside the while-loop
>    - bytes_compl is also needed for future BQL support
> 2. When bcmgenet device uses Tx checksum offload, each transmitted
>    skb has an extra 64-byte header prepended to it. This needs to
>    be deducted when counting transmitted bytes.
> 3. skb->len covers the entire length of skb, whether it is linear or
>    fragmented. Thus, when we clean the fragments, do not increase
>    transmitted bytes.
> 
> Signed-off-by: Petri Gynther <pgynther@...gle.com>
> ---
>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index 6746fd0..9990582 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -1171,6 +1171,7 @@ static unsigned int __bcmgenet_tx_reclaim(struct net_device *dev,
>  	struct enet_cb *tx_cb_ptr;
>  	struct netdev_queue *txq;
>  	unsigned int pkts_compl = 0;
> +	unsigned int bytes_compl = 0;
>  	unsigned int c_index;
>  	unsigned int txbds_ready;
>  	unsigned int txbds_processed = 0;
> @@ -1193,16 +1194,14 @@ static unsigned int __bcmgenet_tx_reclaim(struct net_device *dev,
>  		tx_cb_ptr = &priv->tx_cbs[ring->clean_ptr];
>  		if (tx_cb_ptr->skb) {
>  			pkts_compl++;
> -			dev->stats.tx_packets++;
> -			dev->stats.tx_bytes += tx_cb_ptr->skb->len;
> +			bytes_compl += tx_cb_ptr->skb->len -
> +				       (priv->desc_64b_en ? 64 : 0);

Please do not use this 64 scalar, prefer sizeof(struct status_64)

I know this driver uses skb_pull(skb, 64); len -= 64; in
bcmgenet_desc_rx(), but I would prefer not adding magic values.

Thanks.