netdev - Re: [PATCH 4/4] USBNET: ax88179_178a: enable tso if host supports sg dma

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Date:	Thu, 1 Aug 2013 16:10:48 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Oliver Neukum <oneukum@...e.de>,
	Freddy Xin <freddy@...x.com.tw>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Grant Grundler <grundler@...gle.com>, netdev@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH 4/4] USBNET: ax88179_178a: enable tso if host supports sg dma

On Thu, Aug 1, 2013 at 1:04 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2013-08-01 at 12:41 +0800, Ming Lei wrote:
>
>> From my trace result, lots of linear SKBs are cloned or header-cloned, so
>> it needs skb copy too.
>>
>> Is it normal in xmit path to see cloned SKBs for driver? If not, I can add check
>> to avoid allocation of 8 bytes header for non-cloned skb.
>
> Existing code is not very friendly and very complex.
>
> Sure TCP stack does a clone for every skb from socket write queue,
> but header should be available for pushing 8 bytes.
>
> The !skb_cloned(skb) test should be removed if the memmove() is not
> needed.
>
> Could you try following patch ?

Tested-by: Ming Lei <ming.lei@...onical.com>

This patch does work, and it will make the patch 4/4 become very
simple, :-)

I will rewrite this one against your patch.

Thanks,
--
Ming Lei
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