netdev - Re: [PATCH net-next 0/3] openvswitch: Add STT support.

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Date:	Fri, 23 Jan 2015 09:38:32 -0800
From:	Jesse Gross <jesse@...ira.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Pravin B Shelar <pshelar@...ira.com>,
	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 0/3] openvswitch: Add STT support.

On Fri, Jan 23, 2015 at 8:58 AM, Tom Herbert <therbert@...gle.com> wrote:
> On Tue, Jan 20, 2015 at 12:25 PM, Pravin B Shelar <pshelar@...ira.com> wrote:
>> Following patch series adds support for Stateless Transport
>> Tunneling protocol.
>> STT uses TCP segmentation offload available in most of NIC. On
>> packet xmit STT driver appends STT header along with TCP header
>> to the packet. For GSO packet GSO parameters are set according
>> to tunnel configuration and packet is handed over to networking
>> stack. This allows use of segmentation offload available in NICs
>>
>> Netperf unidirectional test gives ~9.4 Gbits/s performance on 10Gbit
>> NIC with 1500 byte MTU with two TCP streams.
>>
> The reason you're able to get 9.4 Gbit/s with an L2 encapsulation
> using STT is that it has less protocol overhead per packet when doing
> segmentation compared to VXLAN (without segmentation STT packets will
> have more overhead than VXLAN).
>
> A VXLAN packet with TCP/IP has headers
> IP|UDP|VXLAN|Ethernet|IP|TCP+options. Assuming TCP is stuffed with
> options, this is 20+8+8+16+20+40=112 bytes, or 7.4% MTU. Each STT
> segment created in GSO, other than the first, has just IP|TCP headers
> which is 20+20=40 bytes or 2.6% MTU. So this explains throughput
> differences between VXLAN and STT.

Tom, what performance do you see with a single stream of VXLAN running
on net-next with default configuration? The difference in numbers
being posted here is greater than a few percent caused by protocol
overheard.
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