From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexander Duyck <alexander.h.duyck@intel.com>
Subject: Re: Low performance Intel 10GE NIC (3.2.10) on 2.6.38 Kernel
Date: Thu, 07 Apr 2011 08:58:59 -0700
Message-ID: <4D9DDF43.9080302@intel.com>
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Cc: Wei Gu <wei.gu@ericsson.com>, netdev <netdev@vger.kernel.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@intel.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
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On 4/7/2011 4:46 AM, Eric Dumazet wrote:
> Le jeudi 07 avril 2011 =C3=A0 19:15 +0800, Wei Gu a =C3=A9crit :
>> Hi,
>> I compile the ixgbe driver into the kernel and run the test again an=
d also change the copy to clone in the fw hook
>> This is the perf report while I was forwarding 150Kpps with
>> The attached file include the basic info about my test system. Pleas=
e let me know if I did some thing wrong.
>>
>> +     71.91%          swapper  [kernel.kallsyms]            [k] poll=
_idle
>> +     10.43%          swapper  [kernel.kallsyms]            [k] inte=
l_idle
>> -      8.00%     ksoftirqd/24  [kernel.kallsyms]            [k] _raw=
_spin_unlock_irqrestore
>> \u2592   - _raw_spin_unlock_irqrestore
>> \u2592      - 42.25% alloc_iova
>> \u2592           intel_alloc_iova
>> \u2592           __intel_map_single
>> \u2592           intel_map_page

I'm almost certain this is the issue here.  I am pretty sure the=20
intel_map_page call indicates that you are running with the Intel IOMMU=
=20
enabled.  As Eric suggested you can either rebuild your kernel with=20
"CONFIG_DMAR=3DN", or pass the kernel the parameter "intel_iommu=3Doff"=
 in=20
order to disable it so that it will instead just use SWIOTLB.

Thanks,

Alex