Subject: Re: 2.6.19-rc1: Volanomark slowdown
From: Arjan van de Ven <arjan@infradead.org>
To: tim.c.chen@linux.intel.com
Cc: linux-kernel@vger.kernel.org, davem@sunset.davemloft.net,
       kuznet@ms2.inr.ac.ru, netdev@vger.kernel.org
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Organization: Intel International BV
Date: Wed, 08 Nov 2006 16:55:18 +0100
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On Tue, 2006-11-07 at 10:32 -0800, Tim Chen wrote:
> The patch
> 
> [TCP]: Send ACKs each 2nd received segment
> commit: 1ef9696c909060ccdae3ade245ca88692b49285b
> http://kernel.org/git/?
> p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1ef9696c909060ccdae3ade245ca88692b49285b
> 
> reduced Volanomark benchmark throughput by 10%.  
> This is because Volanomark sends 
> short message (<100 bytes) on its TCP
> connections.  This patch increases the number of ACKs 
> traffic by 3.5 times.  
> 
> By adopting this patch, we assume that with
> small segment, having short delay is important 
> enough that we are willing to reduce bandwidth 
> with more ACKs.  

I wonder if it's an option to use low priority QoS fields for these acks
(heck I don't even know if ACKs have such fields in their packet) so
that they can get dropped if there are more packets then there is
bandwidth ....


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