From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: Low performance Intel 10GE NIC (3.2.10) on 2.6.38 Kernel
Date: Thu, 14 Apr 2011 18:57:01 +0200
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	 <1302267400.4409.22.camel@edumazet-laptop>
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Cc: Alexander Duyck <alexander.h.duyck@intel.com>,
	Wei Gu <wei.gu@ericsson.com>, netdev <netdev@vger.kernel.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@intel.com>,
	Mike Galbraith <efault@gmx.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Le jeudi 14 avril 2011 =C3=A0 18:56 +0200, Peter Zijlstra a =C3=A9crit =
:
> On Thu, 2011-04-14 at 09:42 -0700, Alexander Duyck wrote:
>=20
> > I'm doing some more digging into this now.  One thought that occurr=
ed to=20
> > me is that if the patch you mention is having some sort of effect t=
his=20
> > could be a sign of perhaps a kernel timer or scheduling problem.
>=20
> Right, so the removal of the NO_HZ throttle will allow the CPU to go
> into C states more often, this could result in longer wake-up times f=
or
> IRQs.
>=20
> We reverted because:
>   - it caused significant battery drain due to not going into C state=
s
>     often enough, and
>   - its a much better idea to implement these things in the idle
>     governor since it already has the job of guestimating the idle
>     duration.
>=20
> I really can't remember back far enough to even come up with a theory=
 of
> why kernels prior to merging the NO_HZ throttle would not exhibit thi=
s
> problem.
>=20
>=20
>=20

Normally, Wei Gu already asked to not use C states.

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01804533/c0180=
4533.pdf

How can we/he check this ?