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

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 7 Nov 2013 07:56:33 +0200

On Wed, Nov 06, 2013 at 06:02:38PM -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.
> 
> > 
> > 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.
> 

I considered doing this but won't this mean packets can get reordered?
In practice we need to maintain ordering of RX frames within
a given flow, correct?

-- 
MST