Date: Wed, 8 Nov 2006 15:00:07 -0800
From: Stephen Hemminger <shemminger@osdl.org>
To: tim.c.chen@linux.intel.com
Cc: Olaf Kirch <okir@suse.de>, 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
Subject: Re: 2.6.19-rc1: Volanomark slowdown
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On Wed, 08 Nov 2006 14:07:32 -0800
Tim Chen <tim.c.chen@linux.intel.com> wrote:

> 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.
> 

Optimizing for loopback is perversion; perversion can be fun but it gets
to be a obsession then it's sick.

-- 
Stephen Hemminger <shemminger@osdl.org>
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