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Date:	Fri, 23 Jan 2015 12:57:21 -0800
From:	Tom Herbert <>
To:	Jesse Gross <>
Cc:	Pravin B Shelar <>,
	David Miller <>,
	Linux Netdev List <>
Subject: Re: [PATCH net-next 0/3] openvswitch: Add STT support.

On Fri, Jan 23, 2015 at 12:20 PM, Jesse Gross <> wrote:
> On Fri, Jan 23, 2015 at 10:25 AM, Tom Herbert <> wrote:
>> On Fri, Jan 23, 2015 at 9:38 AM, Jesse Gross <> wrote:
>>> On Fri, Jan 23, 2015 at 8:58 AM, Tom Herbert <> wrote:
>>>> On Tue, Jan 20, 2015 at 12:25 PM, Pravin B Shelar <> 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.
>> Please look at the data I posted with the VXLAN RCO patches.
> The data you posted uses 200 streams, so I assume that you are using
> multiple CPUs. It's not surprising that you would be able to consume a
> 10G link in that case. STT can do this with a single stream and less
> than 1 core (or alternately handle higher throughput). Claiming that
> since both can hit 10G they are same is not accurate.
> Discussing performance like this seems a little silly given that the
> code is available. Pravin posted some numbers that he got, if you want
> to dispute them then why don't you just try running it?

Because you haven't provided network interface like I already
requested twice, and I really don't have time or motivation to do
development on your patches or figure out how to do this with OVS. If
you want me to test your patches re-spin them with a network interface
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