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

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Date:	Wed, 06 Nov 2013 18:02:38 -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 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.

> 
> Real systems that run for more than a day do end up with seriously
> fragmented memory.

Sure, but having shallow skbs in the first place help quite a bit.

There is no perfect solution, unless of course you change virtio_net to
provide different queues, with different frag sizes.

Sort of what NIU driver uses.


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