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<p class="MsoNormal">Hi list,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m working under CentOS 6.4 + Havana + Neutron + OVS + gre.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m testing performance for gre.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have a 10Gb/s NIC for compute Node.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">While, the max bandwidth I can get is small then 3Gb/s, even I have enough instances.<o:p></o:p></p>
<p class="MsoNormal">I noticed the reason the bandwidth can’t reach higher is due to the utilization for one CPU core is already 100%.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">So, I want to try if I can get higher bandwidth if I have bigger MTU, because the default MTU = 1500.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">But, after I set <b><span style="color:red">network_device_mtu=8500</span></b><span style="color:red">
</span>in "/etc/nova/nova.conf", and restart openstack-nova-compute service and re-create a new instance, the MTU for devices is still 1500:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:.5in">202: qbr053ac004-d6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu
<b><span style="color:red">1500</span></b><span style="color:red"> </span>qdisc noqueue state UNKNOWN<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"> link/ether da:c0:8d:c2:d5:1c brd ff:ff:ff:ff:ff:ff<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">203: qvo053ac004-d6: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu
<b><span style="color:red">1500</span></b><span style="color:red"> </span>qdisc pfifo_fast state UP qlen 1000<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"> link/ether f6:0b:04:3f:9d:41 brd ff:ff:ff:ff:ff:ff<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">204: qvb053ac004-d6: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu
<b><span style="color:red">1500</span></b><span style="color:red"> </span>qdisc pfifo_fast state UP qlen 1000<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"> link/ether da:c0:8d:c2:d5:1c brd ff:ff:ff:ff:ff:ff<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">205: tap053ac004-d6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu
<b><span style="color:red">1500</span></b><span style="color:red"> </span>qdisc htb state UNKNOWN qlen 500<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"> link/ether fe:18:3e:c2:e9:84 brd ff:ff:ff:ff:ff:ff<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Anyone know why is this happen ?<o:p></o:p></p>
<p class="MsoNormal">How can I solve it ??<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks.<o:p></o:p></p>
<p class="MsoNormal">-chen<o:p></o:p></p>
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