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: Fri, 08 Apr 2011 11:49:18 +0200
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Cc: Alexander Duyck <alexander.h.duyck@intel.com>,
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To: Wei Gu <wei.gu@ericsson.com>
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Le vendredi 08 avril 2011 =C3=A0 17:15 +0800, Wei Gu a =C3=A9crit :
> Yeap, you are right, right now I will try the CONFIG_DMAR off:)
>=20
> If you guys know the relation between CONFIG_DMAR and CONFIG_DMAR_DEF=
AULT_ON, please let me know:)


CONFIG_DMAR_DEFAULT_ON is ON by default since linux-2.6.29 and commit

commit f6be37fdc62d0c0214bc49815d1180ebfbd716e2
Author: Kyle McMartin <kyle@redhat.com>
Date:   Thu Feb 26 12:57:56 2009 -0500

    x86: enable DMAR by default
   =20
    Now that the obvious bugs have been worked out, specifically
    the iwlagn issue, and the write buffer errata, DMAR should be safe
    to turn back on by default. (We've had it on since those patches
were
    first written a few weeks ago, without any noticeable bug reports
    (most have been due to the dma-api debug patchset.))
   =20
    Signed-off-by: Kyle McMartin <kyle@redhat.com>
    Acked-by: David Woodhouse <David.Woodhouse@intel.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9c39095..bc2fbad 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1803,7 +1803,7 @@ config DMAR
          remapping devices.
=20
 config DMAR_DEFAULT_ON
-       def_bool n
+       def_bool y
        prompt "Enable DMA Remapping Devices by default"
        depends on DMAR
        help


git describe --contains f6be37fd
v2.6.29-rc7~24^2


But the .config used to build your 2.6.32 kernel, had it set to OFF