netdev - Re: [PATCH 1/2 net-next] ixgbe: use skb

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Date:	Mon, 18 Jun 2012 14:18:47 -0700
From:	Alexander Duyck <alexander.h.duyck@...el.com>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	Greg Rose <gregory.v.rose@...el.com>,
	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2 net-next] ixgbe: use skb_padto

On 06/18/2012 10:58 AM, Stephen Hemminger wrote:
> The code to pad packets here is the same effective code as
> the existing inline function skb_padto(). There is a minor
> performance gain since skb_padto() also uses unlikely().
>
> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>
>
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c	2012-06-18 10:53:09.130376800 -0700
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c	2012-06-18 10:55:13.104540844 -0700
> @@ -6389,11 +6389,8 @@ static netdev_tx_t ixgbe_xmit_frame(stru
>  	 * The minimum packet size for olinfo paylen is 17 so pad the skb
>  	 * in order to meet this minimum size requirement.
>  	 */
> -	if (skb->len < 17) {
> -		if (skb_padto(skb, 17))
> -			return NETDEV_TX_OK;
> -		skb->len = 17;
> -	}
> +	if (skb_padto(skb, 17))
> +		return NETDEV_TX_OK;
>  
>  	tx_ring = adapter->tx_ring[skb->queue_mapping];
>  	return ixgbe_xmit_frame_ring(skb, adapter, tx_ring);
I don't think this will work.  We need to update the skb->len and last I
knew skb_padto doesn't do that.

Thanks,

Alex
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