netdev - Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility workaround (fwd)

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Message-ID: <48e3a4e5.0d1d640a.4cd3.06e9@mx.google.com>
Date:	Wed, 1 Oct 2008 13:27:10 -0300
From:	Dâniel Fraga <fragabr@...il.com>
To:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
Cc:	tglx@...utronix.de, David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility
 workaround (fwd)

On Wed, 1 Oct 2008 15:52:19 +0300 (EEST)
"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> wrote:

> Hi Daniel,
> 
> I forward part of the details to public knowledge (and for Thomas mainly).
> 
> I also put the epoll & accept only log available for him at
> http://www.cs.helsinki.fi/u/ijjarvin/tcp/epoll_accept.txt
> as it won't contain encryption key, etc. related bits.
> 
> Can you Daniel please confirm what exactly was the status about the effect 
> of disabling ntpd?

	Hi Ilpo, ok, thanks. Following suggestion of kernel developers
from bugzilla, I tested with 2.6.27-rc7 and 2.6.27-rc8. The problem
happens less frequently, but still happens.

	Disabling ntpd helps to not "trigger" the problem often. With
ntpd enabled the problem happens at least once a day. Without ntpd, it
doesn't happen anymore or seldom happens. Disabling high resolution
timers helps too.

	I'll follow your previous suggestions, but I didn't have time
yet. If anyone needs more info, just ask. Thanks.

	Ps: just to clarify for Thomas. The problem has started in
2.6.25 kernel and remain in 2.6.26 until now (2.6.27-rc8). Something
(probably related to timers) changed in 2.6.25 which causes this,
although the effect is seem on network stalling.


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