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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