From: Oleksandr Natalenko <oleksandr@natalenko.name>
To: Neal Cardwell <ncardwell@google.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
Netdev <netdev@vger.kernel.org>,
Yuchung Cheng <ycheng@google.com>
Subject: Re: [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c
Date: Fri, 15 Sep 2017 21:04:36 +0200 [thread overview]
Message-ID: <12759907.teKvueDKTR@natalenko.name> (raw)
In-Reply-To: <CADVnQymkqE+mt4OwtkL1ddpRbqJYPH8CJ0JhNn6ML9YPJdCJxA@mail.gmail.com>
Hello.
With net.ipv4.tcp_fack set to 0 the warning still appears:
===
» sysctl net.ipv4.tcp_fack
net.ipv4.tcp_fack = 0
» LC_TIME=C dmesg -T | grep WARNING
[Fri Sep 15 20:40:30 2017] WARNING: CPU: 1 PID: 711 at net/ipv4/tcp_input.c:
2826 tcp_fastretrans_alert+0x7c8/0x990
[Fri Sep 15 20:40:30 2017] WARNING: CPU: 0 PID: 711 at net/ipv4/tcp_input.c:
2826 tcp_fastretrans_alert+0x7c8/0x990
[Fri Sep 15 20:48:37 2017] WARNING: CPU: 1 PID: 711 at net/ipv4/tcp_input.c:
2826 tcp_fastretrans_alert+0x7c8/0x990
[Fri Sep 15 20:48:55 2017] WARNING: CPU: 0 PID: 711 at net/ipv4/tcp_input.c:
2826 tcp_fastretrans_alert+0x7c8/0x990
» ps -up 711
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 711 4.3 0.0 0 0 ? S 18:12 7:23 [irq/123-
enp3s0]
===
Any suggestions?
On pátek 15. září 2017 16:03:00 CEST Neal Cardwell wrote:
> Thanks for testing that. That is a very useful data point.
>
> I was able to cook up a packetdrill test that could put the connection
> in CA_Disorder with retransmitted packets out, but not in CA_Open. So
> we do not yet have a test case to reproduce this.
>
> We do not see this warning on our fleet at Google. One significant
> difference I see between our environment and yours is that it seems
> you run with FACK enabled:
>
> net.ipv4.tcp_fack = 1
>
> Note that FACK was disabled by default (since it was replaced by RACK)
> between kernel v4.10 and v4.11. And this is exactly the time when this
> bug started manifesting itself for you and some others, but not our
> fleet. So my new working hypothesis would be that this warning is due
> to a behavior that only shows up in kernels >=4.11 when FACK is
> enabled.
>
> Would you be able to disable FACK ("sysctl net.ipv4.tcp_fack=0" at
> boot, or net.ipv4.tcp_fack=0 in /etc/sysctl.conf, or equivalent),
> reboot, and test the kernel for a few days to see if the warning still
> pops up?
>
> thanks,
> neal
>
> [ps: apologies for the previous, mis-formatted post...]
next prev parent reply other threads:[~2017-09-15 19:04 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-10 20:53 [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c Oleksandr Natalenko
2017-09-10 23:59 ` Neal Cardwell
2017-09-15 5:03 ` Oleksandr Natalenko
2017-09-15 14:03 ` Neal Cardwell
2017-09-15 19:04 ` Oleksandr Natalenko [this message]
2017-09-17 18:43 ` Oleksandr Natalenko
2017-09-18 17:18 ` Yuchung Cheng
2017-09-18 17:51 ` Yuchung Cheng
2017-09-18 17:59 ` Oleksandr Natalenko
2017-09-18 18:01 ` Yuchung Cheng
2017-09-18 18:04 ` Oleksandr Natalenko
2017-09-18 20:41 ` Oleksandr Natalenko
2017-09-18 20:46 ` Oleksandr Natalenko
2017-09-18 21:40 ` Yuchung Cheng
2017-09-19 11:04 ` Oleksandr Natalenko
2017-09-19 18:16 ` Yuchung Cheng
2017-09-19 16:05 ` Oleksandr Natalenko
2017-09-21 1:46 Roman Gushchin
2017-09-21 17:07 ` Yuchung Cheng
[not found] ` <CAK6E8=cGF+xKiixRVvA=3PVPA7OQta9hVLTgCbKgvYf3e9Eu-A@mail.gmail.com>
2017-09-26 13:10 ` Roman Gushchin
2017-09-27 0:12 ` Yuchung Cheng
2017-09-27 0:18 ` Yuchung Cheng
2017-09-28 8:14 ` Oleksandr Natalenko
2017-09-28 23:36 ` Yuchung Cheng
2017-10-26 2:07 ` Alexei Starovoitov
2017-10-26 5:37 ` Yuchung Cheng
2017-10-27 20:38 ` Eric Dumazet
2017-11-06 22:27 ` Yuchung Cheng
2017-11-10 13:15 ` Oleksandr Natalenko
2017-11-10 13:40 ` Oleksandr Natalenko
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