[ovs-discuss] low bandwidth for gre

[Li, Chen]

Yes, fragmentation do affect the bandwidth.

I run command  to change interfaces' MTU size to test if fragmentation makes a difference.
        ifconfig eth4 mtu ${mtu_size}
        ifconfig br-int mtu ${mtu_size}

The default MTU = 1500    =>    122 Kbits/sec
                    MTU = 3000    =>     419 Kbits/sec 
                    MTU = 6000    =>     780 Kbits/sec
                    MTU = 9000    =>     1.14 Mbits/sec


But, what I don’t understand is, I didn’t see really high CPU%.

Also, there is no other way to improve the bandwidth ?
Even under MTU=9000, 1.14 Mb/s vs. 10 Gb/s, the gap between the test result we can get and the physical NIC is unacceptable!!


Thanks.
-chen


-----Original Message-----
From: Jesse Gross [mailto:jesse at nicira.com] 
Sent: Tuesday, January 07, 2014 10:32 AM
To: Li, Chen
Cc: discuss at openvswitch.org
Subject: Re: [ovs-discuss] low bandwidth for gre

Well did you at least see if fragmentation makes a difference?

On Mon, Jan 6, 2014 at 8:14 PM, Li, Chen <chen.li at intel.com> wrote:
> But 122 Kbits/s vs. 9.41Gb/s ??
>
> Is this correct ???
>
> How can I improve it ??
>
>
> Thanks.
> -chen
>
>
> -----Original Message-----
> From: Jesse Gross [mailto:jesse at nicira.com]
> Sent: Tuesday, January 07, 2014 12:24 AM
> To: Li, Chen
> Cc: discuss at openvswitch.org
> Subject: Re: [ovs-discuss] low bandwidth for gre
>
> On Sun, Jan 5, 2014 at 11:58 PM, Li, Chen <chen.li at intel.com> wrote:
>> Hi list,
>>
>>
>>
>> I’m working under CentOS, so the kernel is 
>> 2.6.32-358.123.2.openstack.el6.x86_64.
>>
>> openvswitch.x86_64      1.11.0_8ce28d-1.el6ost
>>
>>
>>
>> I have two physical machine in the test, each of them have a 10 Gb NIC card.
>>
>> The bandwidth between the two machine using iperf can achieve 9.41Gb/s.
>>
>>
>>
>> After enable gre follow guide
>> http://networkstatic.net/configuring-vxlan-and-gre-tunnels-on-openvsw
>> i
>> tch/#!prettyPhoto
>>
>> The bandwitdth between the two nodes are really low.
>>
>> Only  122 Kbits/s !!!!
>
> At a minimum, fragmentation is presumably occurring.