netdev - Re: [PATCH net-next 3/3] ipv4: gre: add GRO capability

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Message-ID: <CAEP_g=_nSb-ite51PM-E8SY53yOPiZs8N3gDrYNc0L4OU2Ht=A@mail.gmail.com>
Date:	Mon, 1 Oct 2012 13:56:14 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 3/3] ipv4: gre: add GRO capability

On Fri, Sep 28, 2012 at 7:04 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2012-09-27 at 15:03 -0700, Jesse Gross wrote:
>
>> We wouldn't actually do the decapsulation at the point of GRO.  This
>> is actually pretty similar to what we do with TCP - we merge TCP
>> payloads even though we haven't done any real IP processing yet.
>> However, we do check firewall rules later if we actually hit the IP
>> stack.  GRE would work the same way in this case.
>>
>> What I'm describing is pretty much exactly what NICs will be doing, so
>> if that doesn't work we'll have a problem...
>
> GRO ability to truly aggregate data is kind of limited to some
> workloads. How NICs will handle interleaved flows I dont really know.
>
> What you describe needs a serious GRO preliminary work, because it
> depends on napi_gro_flush() being called from time to time, while we
> need something else, more fine grained.
>
> (I am pretty sure GRO needs some love from us, it looks like some
> packets can stay a long time in gro_list. It would be nice if it was
> able to reorder packets (from same flow) as well)

It's definitely possible to improve GRO in a couple of areas.  I'm not
quite sure why you say that these changes are related to tunnels
though, since they're not really different from say, a VLAN tag.

> Anyway, my changes are self-contained in a new file and non intrusive.
>
> As soon as we can provide a better alternative we can revert them ?

Sure, I don't have a problem with your patches for now.  I was just
trying to think about different approaches.
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