netdev - Re: kernel warning in tcp

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Message-ID: <CADVnQy=-ADK-LVVhOC8Fs=z_1PiLjMSc4+z_qnKXu-wKx7Nq8g@mail.gmail.com>
Date:	Mon, 10 Aug 2015 14:35:37 -0400
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Jovi Zhangwei <jovi@...udflare.com>
Cc:	Martin KaFai Lau <kafai@...com>,
	Eric Dumazet <edumazet@...gle.com>,
	Netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	FB Kernel Team <kernel-team@...com>
Subject: Re: kernel warning in tcp_fragment

On Mon, Aug 10, 2015 at 2:10 PM, Jovi Zhangwei <jovi@...udflare.com> wrote:
>
> Ping?
>
> We saw a lot of this warnings in our production system. It would be
> great appreciate if someone can give us the fix on this warnings. :)

What is your net.ipv4.tcp_mtu_probing setting? If 1, have you tried
setting it to 0? Previous reports (
https://patchwork.ozlabs.org/patch/480882/ ) have shown that this gets
rid of at least one source of the warning. So that would provide a
useful data point.

Separately, you could also try the attached patch. This is against
3.14.39. It tries to attack a different possible source of this
warning. Please let us know if that patch helps.

Thanks!

neal

Download attachment "0001-RFC-for-tests-on-v3.14.39-tcp-resegment-skbs-that-we.patch" of type "application/octet-stream" (4569 bytes)