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From: Grant Zhang <gzhang@fastly•com>
To: Martin KaFai Lau <kafai@fb•com>
Cc: netdev <netdev@vger•kernel.org>,
	Neal Cardwell <ncardwell@google•com>,
	Yuchung Cheng <ycheng@google•com>,
	Eric Dumazet <edumazet@google•com>,
	Kernel Team <kernel-team@fb•com>
Subject: Re: Recurring trace from tcp_fragment()
Date: Thu, 04 Jun 2015 13:10:26 -0700	[thread overview]
Message-ID: <5570B0B2.5080908@fastly.com> (raw)
In-Reply-To: <20150604193838.GA2951343@devbig242.prn2.facebook.com>

Hi Martin,

Thank you! My net.ipv4.tcp_mtu_probing is 1. After turning it off, the 
WARN_ON stack is gone.

Could you elaborate a bit on why this setting relates to the WARN_ON 
trace? And what are the pros/cons for disabling mtu_probing?

Thanks,

Grant

On 6/4/15 12:38 PM, Martin KaFai Lau wrote:
> 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
>

next prev parent reply	other threads:[~2015-06-04 20:10 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-29 19:21 Recurring trace from tcp_fragment() Grant Zhang
2015-05-29 19:46 ` Neal Cardwell
2015-05-29 19:53   ` Grant Zhang
2015-05-30 17:29     ` Neal Cardwell
2015-05-30 18:52       ` Grant Zhang
2015-05-30 23:08         ` Neal Cardwell
2015-06-04 16:35           ` Grant Zhang
2015-06-04 19:34             ` Neal Cardwell
2015-06-04 19:38             ` Martin KaFai Lau
2015-06-04 20:10               ` Grant Zhang [this message]
2015-06-04 20:56                 ` Martin KaFai Lau
2015-06-04 21:29                   ` Yuchung Cheng

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