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

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Message-ID: <20080911151222.0ce12158@tux>
Date:	Thu, 11 Sep 2008 15:12:22 -0300
From:	Dâniel Fraga <fragabr@...il.com>
To:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
Cc:	David Miller <davem@...emloft.net>, thomas.jarosch@...ra2net.com,
	billfink@...dspring.com, Netdev <netdev@...r.kernel.org>,
	Patrick Hardy <kaber@...sh.net>,
	netfilter-devel@...r.kernel.org, kadlec@...ckhole.kfki.hu
Subject: Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility
 workaround

On Thu, 11 Sep 2008 16:44:20 +0300 (EEST)
"Ilpo Järvinen" <ilpo.jarvinen@...sinki.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.
> 
> 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.

	Well, I have a new suspect now: ntpd. It seems that when ntpd
syncs the clock, the problem happens (just a guess):

Sep 11 13:55:31 tux ntpd[2652]: synchronized to 143.107.255.15, stratum 2 
Sep 11 13:55:31 tux ntpd[2652]: kernel time sync enabled 0001

	I disabled ntpd (and I'll just sync the clock with ntpdate just one 
time at the boot) and see what happens. I think the problem could be related
to this, since "sudo" is affected too and as far as I know, sudo is very 
sensible to timer.


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