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Date:      Thu, 24 May 2012 17:48:23 -0700
From:      Kevin Oberman <kob6558@gmail.com>
To:        "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>
Cc:        net@freebsd.org
Subject:   Re: Major performance hit with ToS setting
Message-ID:  <CAN6yY1tSLqQMg5LqrPOJ32Y2S2f65yhhCPOdn5VU0NL=VXvONg@mail.gmail.com>
In-Reply-To: <FC59CF19-C3BD-4906-8338-C18AC5DC6867@lists.zabbadoz.net>
References:  <CAN6yY1sLxFJ18ANO7nQqLetnJiT-K6pHC-X3yT1dWuWGa0VLUg@mail.gmail.com> <FC59CF19-C3BD-4906-8338-C18AC5DC6867@lists.zabbadoz.net>

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On Thu, May 24, 2012 at 4:43 PM, Bjoern A. Zeeb
<bzeeb-lists@lists.zabbadoz.net> wrote:
> On 24. May 2012, at 22:55 , Kevin Oberman wrote:
>
>> When we set the ToS bits for less than best effort (also called
>> scavenger) on packets (ToS=3D32), performance on FreeBSD 8.2 is
>> terrible. It was as good as best effort on FreeBSD 7.3 (assuming no
>> congestion). I will look into what 9 does, but does anyone have an
>> idea of why 8.2 behaves so badly when ToS is set to 32?
>> Here is an example of what happens to performance:
>> nuttcp with ToS=3D0:
>> 622.5000 MB / =A0 1.00 sec =3D 5221.7570 Mbps
>> 623.3125 MB / =A0 1.00 sec =3D 5228.5883 Mbps
>> 624.0000 MB / =A0 1.00 sec =3D 5234.4495 Mbps
>>
>> With ToS=3D32 (0x20):
>> 0.3750 MB / =A0 1.00 sec =3D =A0 =A03.1457 Mbps
>> 0.5000 MB / =A0 1.00 sec =3D =A0 =A04.1942 Mbps
>> 0.5000 MB / =A0 1.00 sec =3D =A0 =A04.1942 Mbps
>>
>> This is,of course, on a 10G interface. On 7.3 there is little
>> difference between the two. We are using cubic CC on the 8.2 system.
>
> This looks like a different problem than just TOS. =A0I assume however
> that not setting the TOS you get the same as expected performance?
>
> Which NIC?

The two nuttcp runs were identical and we got similar results with iperf.

All tests were using Myricom (mxge) cards.
--=20
R. Kevin Oberman, Network Engineer
E-mail: kob6558@gmail.com



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