From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?ISO-8859-1?Q?D=E2niel?= Fraga <fragabr@gmail.com>
Subject: Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility
 workaround
Date: Thu, 11 Sep 2008 14:30:06 -0300
Message-ID: <20080911143006.2f516569@tux>
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Cc: David Miller <davem@davemloft.net>, thomas.jarosch@intra2net.com,
	billfink@mindspring.com, Netdev <netdev@vger.kernel.org>,
	Patrick Hardy <kaber@trash.net>,
	netfilter-devel@vger.kernel.org, kadlec@blackhole.kfki.hu
To: "Ilpo =?ISO-8859-1?Q?J=E4rvinen?=" <ilpo.jarvinen@helsinki.fi>
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On Thu, 11 Sep 2008 16:44:20 +0300 (EEST)
"Ilpo J=E4rvinen" <ilpo.jarvinen@helsinki.fi> wrote:

> ...I guess it would be possible to remove SCHED_FEAT_HRTICK from
> /proc/sys/kernel/sched_features then while keeping the hrtimers
> otherwise enabled to test this.
>=20
> It's possible that hrtimers just affect on how easy it is to trigger
> but at least it seems an useful lead until proven otherwise.

	You're right Ilpo. After days and days without the problem,
today it triggered (but I wasn't online at the time, so I couldn't grab
any data).

	So, you're correct. HRtimers just affect on how easy it is to
trigger the issue. In other words: with high resolution timer enabled,
the problem appears more frequently.

	At least if we discovered a way how to trigger this, we could
test it more easily. The problem is to wait a long time for it to
happen.

	Just a curiosity: on your servers, do you use x86_64? It seems
this problem is very specific to x86_64 or appear more often on x86_64
than x86_32. It never happens on my x86_32 bit servers.

=09


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