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

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Message-ID: <1383790120.2878.36.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 06 Nov 2013 18:08:40 -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, mst@...hat.com,
	Jason Wang <jasowang@...hat.com>
Subject: Re: gso: Attempt to handle mega-GRO packets

On Wed, 2013-11-06 at 18:02 -0800, Eric Dumazet wrote:
> On Thu, 2013-11-07 at 09:47 +0800, Herbert Xu wrote:
> 
> > Say the system is fragmented sufficiently that you'll end up with
> > 0-order pages.  In that case you'll only ever be able to coalesce
> > two packets.
> 
> 4K page will contain 2 frags and they will coalesce.
> 
> Performance will still be quite good.
> 
> We probably add a tweak, to not have any hole in this case.

After skb_page_frag_refill() call, its trivial to check if the page is
order-0.

If yes, use the whole remaining space, instead of MAX_PACKET_LEN

-> If memory is fragmented, we switch back to old behavior.

Really, its that simple.





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