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Date:      Thu, 24 May 2012 23:43:42 +0000
From:      "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>
To:        Kevin Oberman <kob6558@gmail.com>
Cc:        net@freebsd.org
Subject:   Re: Major performance hit with ToS setting
Message-ID:  <FC59CF19-C3BD-4906-8338-C18AC5DC6867@lists.zabbadoz.net>
In-Reply-To: <CAN6yY1sLxFJ18ANO7nQqLetnJiT-K6pHC-X3yT1dWuWGa0VLUg@mail.gmail.com>
References:  <CAN6yY1sLxFJ18ANO7nQqLetnJiT-K6pHC-X3yT1dWuWGa0VLUg@mail.gmail.com>

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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=32), 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=0:
> 622.5000 MB /   1.00 sec = 5221.7570 Mbps
> 623.3125 MB /   1.00 sec = 5228.5883 Mbps
> 624.0000 MB /   1.00 sec = 5234.4495 Mbps
> 
> With ToS=32 (0x20):
> 0.3750 MB /   1.00 sec =    3.1457 Mbps
> 0.5000 MB /   1.00 sec =    4.1942 Mbps
> 0.5000 MB /   1.00 sec =    4.1942 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.  I assume however
that not setting the TOS you get the same as expected performance?

Which NIC?

/bz

-- 
Bjoern A. Zeeb                                 You have to have visions!
   It does not matter how good you are. It matters what good you do!




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