netdev - Re: Large performance regression with 6in4 tunnel (sit)

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Date:   Sun, 27 Nov 2016 14:23:40 +1100
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Sven-Haegar Koch <haegar@...net.de>
Cc:     Eli Cooper <elicooper@....com>, netdev@...r.kernel.org,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: Large performance regression with 6in4 tunnel (sit)

Hi Sven-Haegar,

On Fri, 25 Nov 2016 05:06:53 +0100 (CET) Sven-Haegar Koch <haegar@...net.de> wrote:
>
> Somehow this problem description really reminds me of a report on 
> netdev a bit ago, which the following patch fixed:
> 
> commit 9ee6c5dc816aa8256257f2cd4008a9291ec7e985
> Author: Lance Richardson <lrichard@...hat.com>
> Date:   Wed Nov 2 16:36:17 2016 -0400
> 
>     ipv4: allow local fragmentation in ip_finish_output_gso()
>     
>     Some configurations (e.g. geneve interface with default
>     MTU of 1500 over an ethernet interface with 1500 MTU) result
>     in the transmission of packets that exceed the configured MTU.
>     While this should be considered to be a "bad" configuration,
>     it is still allowed and should not result in the sending
>     of packets that exceed the configured MTU.
> 
> Could this be related?
> 
> I suppose it would be difficult to test this patch on this machine?

The kernel I am running on is based on 4.7.8, so the above patch
doesn't come close to applying. Most fo what it is reverting was
introduced in commit 359ebda25aa0 ("net/ipv4: Introduce IPSKB_FRAG_SEGS
bit to inet_skb_parm.flags") in v4.8-rc1.

-- 
Cheers,
Stephen Rothwell