netdev - Re: Recurring trace from tcp

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Message-ID: <20150604193838.GA2951343@devbig242.prn2.facebook.com>
Date:	Thu, 4 Jun 2015 12:38:38 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	Grant Zhang <gzhang@...tly.com>
CC:	netdev <netdev@...r.kernel.org>,
	Neal Cardwell <ncardwell@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Kernel Team <kernel-team@...com>
Subject: Re: Recurring trace from tcp_fragment()

Hi Grant,

On Thu, Jun 04, 2015 at 09:35:04AM -0700, Grant Zhang wrote:
> Hi Neal,
>
> Unfortunately with the patch we still see the same stack trace.
> Attached is the TcpExtTCPSACKReneging with the patch, captured with
> 60 seconds interval. Its value is incremented at an similar speed as
> before, about 30/minute.
>
> If you want to collect any other data, please feel free to let me know.
>

We are also seeing similar WARN_ON stack in our kernel 4.0 testing.

What is your net.ipv4.tcp_mtu_probing setting?  I am currently testing some
code changes and waiting for some more data.  If it is 1 or 2,
can you help to check whether turning it off (by setting it to 0) will stop the
WARN_ON or not in your environment?  Note that after setting it to 0, you
may need to wait for a while (like a few mins) for the existing probing
activities to quiet down before observing the WARN_ON output.

Thanks,
--Martin
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