netdev - Re: [PATCH 2/2] v2 GRE: Add segmentation offload for GRE

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Date:	Thu, 24 Jan 2013 19:38:16 -0800
From:	Pravin Shelar <pshelar@...ira.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, jesse@...ira.com
Subject: Re: [PATCH 2/2] v2 GRE: Add segmentation offload for GRE

On Thu, Jan 24, 2013 at 5:34 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2013-01-24 at 16:14 -0800, Pravin Shelar wrote:
>
>> I think this patch does fix csum issue without causing any performance
>> regression. So this patch shld be enough to solve GRE-GSO issue. Once
>> you have fix, this code can be optimized even more.
>
> It adds the extra copy, since you assume no SG capability so
> skb_segment() _does_ a copy.
>
OK,I wil use device features.

> As the checksum is needed, its true the copy is almost not noticed,
> but one day NIC will be able to perform the checksum for us.
> (Maybe its already the case for some of them)
>
> I would first fix the checksum issue in a generic way, then
> apply this patch on top of the fix, so that we can use SG and avoid
> the extra copy for the typical tcp_sendmsg()

I thought you were working on the fix. If not I will post patch.
>
> It seems you focus on the TAP use case only, seeing you removed
> code that doesn't work for TAP but do work for regular locally
> terminated flows.
>
I have tested patch with GRE TAP and non TAP devices.

> You did a lot of implementation choices and none of them
> are described in a changelog, making future work a bit hard.
>

ok. I will update changelog.
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