netdev - Re: [RFC] random SYN drops causing connect() delays

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Date:	Tue, 27 Apr 2010 18:56:02 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	tgraf@...radead.org
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC] random SYN drops causing connect() delays

From: Thomas Graf <tgraf@...radead.org>
Date: Mon, 12 Apr 2010 04:39:03 -0400

> On Mon, Apr 12, 2010 at 04:06:33AM -0400, Thomas Graf wrote:
>>  - While the issue is appearing, the acceptq seems to be overflowing. Both
>>    LISTENOVERFLOWS and LISTENDROPS are increasing although not by the exact
>>    number of delay occurences. inetdiag reports sk_max_ack_backlog to be 0
>>    therefore one possibility that comes to mind is that sk_ack_backlog
>>    underflows due to a race.
> 
> Forget about the underflow thought, inetdiag was reporting falsely.
> sk_max_ack_backlog is set to 128 as it should and the listen overflow
> happens normally. Still the fact remains that while the issue is appearing
> listen overflows are counted.

I can't reproduce on my system even with sched_child_runs_first set to '1'.

Are you running identd or something like that which intercepts the connections
to port 22 before 'sshd' actually gets it?
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