netdev - Re: gso: Attempt to handle mega-GRO packets

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Message-ID: <1383786488.2878.18.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 06 Nov 2013 17:08:08 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Ben Hutchings <bhutchings@...arflare.com>,
	David Miller <davem@...emloft.net>,
	christoph.paasch@...ouvain.be, netdev@...r.kernel.org,
	hkchu@...gle.com, mwdalton@...gle.com
Subject: Re: gso: Attempt to handle mega-GRO packets

On Thu, 2013-11-07 at 09:00 +0800, Herbert Xu wrote:
> On Wed, Nov 06, 2013 at 04:56:03PM -0800, Eric Dumazet wrote:
> > On Thu, 2013-11-07 at 08:47 +0800, Herbert Xu wrote:
> > > On Wed, Nov 06, 2013 at 04:15:21PM -0800, Eric Dumazet wrote:
> > > >
> > > > Here is the patch I came into (I tested it and it works very fine)
> > > 
> > > Thanks.  However, unless I'm missing something aren't you now
> > > copying every linear skb frag_list?  With the current code we
> > > just do a clone and add the headers.
> > 
> > No copy at all.
> > 
> > As explained, all RX skb are now backed to a page frag.  (see
> > skb->head_frag)
> 
> Even if we have called pskb_expand_head on it?

Well, in this case we pulled only the headers in skb->head.

Only few buggy drivers do a pull of say 64 bytes in skb->head before
calling eth_type_trans() so could possibly have a few bytes of TCP
payload in skb->head

And this case is handled without copy.




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