netdev - Re: Hit regression with TCP

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Date:	Tue, 17 Nov 2015 04:07:49 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ethan Zhao <ethan.kernel@...il.com>
Cc:	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Hit regression with TCP_TW REUSE/RECYCLE

On Tue, 2015-11-17 at 14:35 +0800, Ethan Zhao wrote:
> Tested the same case with 4.4-RC1, it was fixed in 4.4-RC1.
> But don't know which commit fixed it.
> 
>  # echo 1024 65535 > /proc/sys/net/ipv4/ip_local_port_range
>  # cat /proc/sys/net/ipv4/ip_local_port_range
> 1024    65535
>  # echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse
>  #  cat /proc/sys/net/ipv4/tcp_tw_reuse
> 1
>  # echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle
>  #  cat /proc/sys/net/ipv4/tcp_tw_reuse
> 1
>  # ./accept -n 5 -r &
> [1] 11866
>  # port: 7954
> ninst: 5
> reuseport: 1
> 
>  # ./connect -i 127.0.0.1 -n 5 -d 10
> 78578.50
>  # uname -a
> Linux localhost.localdomain 4.4.0-rc1 #49 SMP Tue Nov 17 15:04:18 KST
> 2015 x86_64 x86_64 x86_64 GNU/Linux

Maybe run a reverse bisection ?

tcp_tw_reuse and tcp_tw_recycle both set to one have never been
supported in linux.

tcp_tw_recycle - BOOLEAN
        Enable fast recycling TIME-WAIT sockets. Default value is 0.
        It should not be changed without advice/request of technical
        experts.

tcp_tw_reuse - BOOLEAN
        Allow to reuse TIME-WAIT sockets for new connections when it is
        safe from protocol viewpoint. Default value is 0.
        It should not be changed without advice/request of technical
        experts.

Thanks.


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