netdev - Re: low vxlan throughput with tso enabled

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Date:	Tue, 03 Feb 2015 08:36:15 -0800
From:	Rick Jones <rick.jones2@...com>
To:	Reiner Herrmann <reiner.herrmann@...hos.com>,
	netdev@...r.kernel.org
CC:	svens@...ckframe.org, Vittorio Curcio <Vittorio.Curcio@...hos.com>
Subject: Re: low vxlan throughput with tso enabled

On 02/03/2015 07:50 AM, Reiner Herrmann wrote:
> I have a vxlan tunnel established between two network interfaces, which
> both have a MTU of 1500. The vxlan interfaces have the same MTU.
> With TSO enabled, I observe low throughput with TCP connections (<100
> kB/s).
> Disabling TSO works around this issue and throughput is as expected.
> Can someone please explain how TSO is influencing the tunnel to cause
> such a difference?

I've been under the impression that one generally wants the MTU of a 
tunnel interface to be no more than the MTU of the physical interface 
over which it runs, less the size of the encapsulation headers used by 
the tunnel.  What happens when you make the MTU of the tunnel interface 
1400 bytes instead of 1500?

rick jones
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