netdev - Re: intel 82599 multi-port performance

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Message-ID: <4E80A2AB.2040206@intel.com>
Date:	Mon, 26 Sep 2011 09:04:59 -0700
From:	Alexander Duyck <alexander.h.duyck@...el.com>
To:	frog1120@...il.com
CC:	"J.Hwan.Kim" <j.hwan.kim99@...il.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: intel 82599 multi-port performance

On 09/26/2011 08:42 AM, J.Hwan.Kim wrote:
> On 2011년 09월 26일 23:20, Chris Friesen wrote:
>> On 09/26/2011 04:26 AM, J.Hwan Kim wrote:
>>> Hi, everyone
>>>
>>> Now, I'm testing a network card including intel 82599.
>>> In our experiment, with the driver modified with ixgbe and multi-port
>>> enabled,
>>
>> What do you mean by "modified with ixgbe and multi-port enabled"? You
>> shouldn't need to do anything special to use both ports.
>>
>>> rx performance of each port with 10Gbps of 64bytes frame is
>>> a half than when only 1 port is used.
>>
>> Sounds like a cpu limitation. What is your cpu usage? How are your
>> interrupts routed? Are you using multiple rx queues?
>>
>
> Our server is XEON 2.4GHz with 8 cores.
> I'm using 4 RSS queues for each port and distributed it's interrupts 
> to different cores respectively.
> I checked the CPU utilization with TOP, I guess ,it is not cpu 
> imitation problem.

What kind of rates are you seeing on a single port versus multiple 
ports?  There are multiple possibilities in terms of what could be 
limiting your performance.

It sounds like you are using a single card, would that be correct?  If 
you are running close to line rate on both ports this could be causing 
you to saturate the PCIe x8 link.  If you have a second card available 
you may want to try installing that in a secondary Gen2 PCIe slot and 
seeing if you can improve the performance by using 2 PCIe slots instead 
of one.

Also could you include your kernel config?  Certain features such as 
Netfilter and IOMMU can have a significant impact on performance.

Thanks,

Alex
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