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Date: Fri, 25 May 2007 11:40:43 +0400
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: Luigi Rizzo <rizzo@icir.org>
Message-ID: <20070525074043.GH89017@glebius.int.ru>
References: <20070524182545.GF89017@FreeBSD.org> <4655EEAD.2060307@freebsd.org>
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Cc: Andre Oppermann <andre@FreeBSD.org>, net@FreeBSD.org
Subject: Re: TCP problems after 124 days of uptime?
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On Thu, May 24, 2007 at 01:52:33PM -0700, Luigi Rizzo wrote:
L> On Thu, May 24, 2007 at 09:59:41PM +0200, Andre Oppermann wrote:
L> > Gleb Smirnoff wrote:
L> > >   Yesterday two of our web servers running 6.2-PRERELEASE experienced
L> > > problems with accepting TCP connections. A small percentage of SYN
L> > > packets was ignored. The packets were seen in tcpdump output, but not
L> > > processed by TCP stack. No accept queue overflows occured, according
L> > > to 'netstat -sp tcp'.
L> > > 
L> > > Failing to find any clue I have rebooted one of them, and after
L> > > reboot is started to work flawlessly. Reboot also helped the second
L> > > one. Both servers were booted at the same time - 124 days ago.
L> > > 
L> > > Any ideas, any similar reports?
L> > 
L> > ticks is a 32 bit signed integer and TCP isn't really aware of it
L> > going negative and rolling over.  This is something I'm working on
L> > fixing in -current.  Haven't analyzed all potential cases there yet.
L> 
L> by chance, is your 'hz' set to 200 ?
L> this might explay something, because 2^31/(86400*200) = 124.275

Nope. hz is default - 1000.

-- 
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE