netdev - Re: [PATCH RFC net-next 00/11] udp gso

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Date:   Wed, 18 Apr 2018 14:12:40 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Network Development <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH RFC net-next 00/11] udp gso

On Wed, Apr 18, 2018 at 1:50 PM, David Miller <davem@...emloft.net> wrote:
> From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> Date: Tue, 17 Apr 2018 16:00:50 -0400
>
>> Segmentation offload reduces cycles/byte for large packets by
>> amortizing the cost of protocol stack traversal.
>>
>> This patchset implements GSO for UDP.
>
> This looks great.
>
> And as mentioned in other emails, the interface looks good too by letting
> the app choose the segmentation point.
>
> It's a real shame we lose checksumming with MSG_MORE, perhaps we can find
> a way to lift that restriction?

Actually, yes, I should be able to relax that constraint with
segmentation.

It is there in case a corked packet may grow to the point of
having to be fragmented. But segmentation already ensures
that its datagrams always fit in MTU.

Should be simple refinement to

            !(flags & MSG_MORE) &&

in __ip_append_data.