Open Stack

Hi Heiko,

I do have tried edit dhcp-option-force in etc/neutron/dnsmasq.conf.
Base on my test, the value dhcp-option-force=26,${MTU} is only affect the MTU in instances, it not affected any virtual port that we found in compute node.
This means, even I set dhcp-option-force=26,9000, you can get MTU=9000 in instances, but due to the virtual ports in host is still have MTU=1500, so the real package size instance will get is still 1500.

Also, I do restricted instance's bandwidth by setting extra_specs in flavor :
nova flavor-show test_flavor
+----------------------------+-----------------------------------------------------------------------------------+
| Property                   | Value                                                                             |
+----------------------------+-----------------------------------------------------------------------------------+
| name                       | test_flavor        |
| ram                        | 512                                                                               |
| OS-FLV-DISABLED:disabled   | False                                                                             |
| vcpus                      | 1                                                                                 |
| extra_specs                | {u'quota:vif_inbound_average': u'51200', u'quota:vif_outbound_average': u'51200'} |
| swap                       |                                                                                   |
| os-flavor-access:is_public | True                                                                              |
| rxtx_factor                | 1.0                                                                               |
| OS-FLV-EXT-DATA:ephemeral  | 0                                                                                 |
| disk                       | 0                                                                                 |
| id                         | 7                                                                                 |
+----------------------------+-----------------------------------------------------------------------------------+

The reason I want to use jumbo frames is I hope jumbo frames will use less CPU%, so that I can get higher bandwidth for a whole compute node.

Thanks.
-chen


-----Original Message-----
From: Heiko Krämer [mailto:info at honeybutcher.de] 
Sent: Monday, January 27, 2014 4:11 PM
To: openstack at lists.openstack.org
Subject: Re: [Openstack] How to enable jumbo frames for instances ?

Hi Chen,

first of all, the default supported network driver for kvm supported only 1g.

You can configure your MTU in your /etc/neutron/dnsmasq.conf on network
node,like:
dhcp-option-force=26,1454

MTU = 1454

You need to kill all dnsmasq processes on your network node and restart dhcp agent.

In addition you ought to consider that is maybe a bad idea to allow each spawned instance to use the complete 10G connection. I'm using for each compute node two 10G Nic's which is one for internal instance communications and the other for storage attachments but every time only 1G to the instances.

Maybe it helps.


Cheers
Heiko

On 27.01.2014 08:39, Li, Chen wrote:
> Hi list,
>
> I'm working under CentOS 6.4 + Havana + Neutron + OVS + gre.
>
> I'm testing performance for gre.
>
> I have a 10Gb/s NIC for compute Node.
>
> While, the max bandwidth I can get is small then 3Gb/s, even I have
enough instances.
> I noticed the reason the bandwidth can't reach higher is due to the
utilization for one CPU core is already 100%.
>
> So, I want to try if I can get higher bandwidth if I have bigger MTU,
because the default MTU = 1500.
>
> But, after I set network_device_mtu=8500 in "/etc/nova/nova.conf", and
restart openstack-nova-compute service and re-create a new instance, the MTU for devices is still 1500:
>
> 202: qbr053ac004-d6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
noqueue state UNKNOWN
>     link/ether da:c0:8d:c2:d5:1c brd ff:ff:ff:ff:ff:ff
> 203: qvo053ac004-d6: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu
1500 qdisc pfifo_fast state UP qlen 1000
>     link/ether f6:0b:04:3f:9d:41 brd ff:ff:ff:ff:ff:ff
> 204: qvb053ac004-d6: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu
1500 qdisc pfifo_fast state UP qlen 1000
>     link/ether da:c0:8d:c2:d5:1c brd ff:ff:ff:ff:ff:ff
> 205: tap053ac004-d6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
htb state UNKNOWN qlen 500
>     link/ether fe:18:3e:c2:e9:84 brd ff:ff:ff:ff:ff:ff
>
> Anyone know why is this happen ?
> How can I solve it ??
>
> Thanks.
> -chen
>
>
>
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