netdev - Re: e1000 full-duplex TCP performance well below wire speed

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Message-ID: <47A1F2D5.5070709@aei.mpg.de>
Date:	Thu, 31 Jan 2008 17:09:57 +0100
From:	Carsten Aulbert <carsten.aulbert@....mpg.de>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Bruce Allen <ballen@...vity.phys.uwm.edu>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	netdev@...r.kernel.org,
	Henning Fehrmann <henning.fehrmann@....mpg.de>,
	Bruce Allen <bruce.allen@....mpg.de>
Subject: Re: e1000 full-duplex TCP performance well below wire speed

Hi Andi,

Andi Kleen wrote:
> Another issue with full duplex TCP not mentioned yet is that if TSO is used 
> the output  will be somewhat bursty and might cause problems with the 
> TCP ACK clock of the other direction because the ACKs would need 
> to squeeze in between full TSO bursts.
> 
> You could try disabling TSO with ethtool.

I just tried that:

https://n0.aei.uni-hannover.de/wiki/index.php/NetworkTestNetperf3

It seems that the numbers do get better (sweet-spot seems to be MTU6000 
with 914 MBit/s and 927 MBit/s), however for other settings the results 
vary a lot so I'm not sure how large the statistical fluctuations are.

Next test I'll try if it makes sense to enlarge the ring buffers.

Thanks

Carsten
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