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Date:   Fri, 24 Mar 2017 13:54:08 -0700
From:   Ben Greear <>
To:     Alexander Duyck <>
Cc:     e1000-devel list <>,
        netdev <>
Subject: Re: Performance issue with igb with lots of different src-ip addrs.

On 03/16/2017 08:51 PM, Ben Greear wrote:
> I think we can, might take us a day or two to get time to do it.
> Thanks,
> Ben
> On 03/16/2017 08:05 PM, Alexander Duyck wrote:
>> I'm not really interested in installing a custom version of pktgen.
>> Any chance you can recreate the issue with standard pktgen?
>> You might try running perf to get a snapshot of what is using CPU time
>> on the system.  It will probably give you a pretty good idea where the
>> code is that is eating up all your CPU time.

So, I had time to dig into this today.

Turns out that our tool was reporting drops because of sequence number
gaps, which in turn were caused by out-of-order frames...not actually
dropping frames.

If I force the rss_queues to one, the problem goes away.

Sorry for mis-reporting a bug.


>> - Alex
>> On Thu, Mar 16, 2017 at 7:46 PM, Ben Greear <> wrote:
>>> I'm actually using a hacked up version of pktgen nicely driven by our
>>> GUI tool, but the crux is that you need to set min and max src IP to some
>>> large
>>> range.
>>> We are driving pktgen from a separate machine.  Stock pktgen isn't good at
>>> reporting
>>> received pkts last I checked, so it may be more difficult to easily view the
>>> problem.
>>> I'll be happy to set up my tool on your Fedora 24 or similar VM or machine
>>> if you
>>> want.
>>> Thanks,
>>> Ben
>>> On 03/16/2017 07:35 PM, Alexander Duyck wrote:
>>>> Can you include the pktgen script you are running?
>>>> Also when you say you are driving traffic through the bridge are you
>>>> sending from something external on the system or are you actually
>>>> directing the traffic from pktgen into the bridge directly?
>>>> - Alex
>>>> On Thu, Mar 16, 2017 at 3:49 PM, Ben Greear <>
>>>> wrote:
>>>>> Hello,
>>>>> We notice that when using two igb ports as a bridge, if we use pktgen to
>>>>> drive traffic through the bridge and randomize (or use a very large
>>>>> range)
>>>>> for the source IP addr in pktgen, then performance of igb is very poor
>>>>> (like
>>>>> 150Mbps
>>>>> throughput instead of 1Gbps).  It runs right at line speed if we use same
>>>>> src/dest
>>>>> IP addr in pktgen.  So, seems it is related to lots of src/dest IP
>>>>> addresses.
>>>>> We see same problem when using pktgen to send to itself, and we see this
>>>>> in
>>>>> several different kernels.  We specifically tested bridge mode in this
>>>>> stock
>>>>> Fedora kernel:
>>>>>  Linux lfo350-59cc 4.9.13-101.fc24.x86_64 #1 SMP Tue Mar 7 23:48:32 UTC
>>>>> 2017
>>>>> x86_64 x86_64 x86_64 GNU/Linux
>>>>> e1000e does not show this problem in our testing.
>>>>> Any ideas what the issue might be and how to fix it?
>>>>> Thanks,
>>>>> Ben
>>>>> --
>>>>> Ben Greear <>
>>>>> Candela Technologies Inc
>>> --
>>> Ben Greear <>
>>> Candela Technologies Inc

Ben Greear <>
Candela Technologies Inc

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