Subject: Re: 2.6.19-rc1: Volanomark slowdown
From: Tim Chen <tim.c.chen@linux.intel.com>
Reply-To: tim.c.chen@linux.intel.com
To: Olaf Kirch <okir@suse.de>
Cc: Arjan van de Ven <arjan@infradead.org>, linux-kernel@vger.kernel.org,
       davem@sunset.davemloft.net, kuznet@ms2.inr.ac.ru,
       netdev@vger.kernel.org
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Organization: Intel
Date: Wed, 08 Nov 2006 14:07:32 -0800
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On Wed, 2006-11-08 at 23:10 +0100, Olaf Kirch wrote:

> 
> In fixing performance issues, the most obvious explanation isn't always
> the right one. It's quite possible you're right, sure.
> 
> What I'm saying though is that it doesn't rhyme with what I've seen of
> Volanomark - we ran 2.6.16 on a 4p Intel box for instance and it didn't
> come close to saturating a Gigabit pipe before it maxed out on CPU load.
> 

I am running Volanomark in a loopback mode on a 2P woodcrest box 
(4 cores).  So the configuration is a bit different.  

In my testing, the CPU utilization is at 100%.  So
increase in ACKs will cost CPU to devote more
time to process those ACKs and reduce throughput.

> 
> You could count the number of outbound packets dropped on the server.
> 

As I'm running in loopback mode, there are no dropped packets.

Thanks.

Tim

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