Hi,All.
    Recently I deploy an Openstack(Mitaka)+OVS(use VLAN isolation) in my lab,but I meet some problem.
Here is my package version:
[root@my1n12nt ~]# uname -r
3.10.0-514.26.2.el7.x86_64
[root@my1n12nt ~]# cat /etc/redhat-release 
CentOS Linux release 7.3.1611 (Core) 
[root@my1n12nt ~]# rpm -qa |grep openvswitch
openvswitch-2.6.1-4.1.git20161206.el7.x86_64
python-openvswitch-2.6.1-4.1.git20161206.el7.noarch
openstack-neutron-openvswitch-8.4.0-1.el7.noarch
[root@my1n12nt ~]# rpm -qa |grep openstack
openstack-neutron-common-8.4.0-1.el7.noarch
openstack-neutron-ml2-8.4.0-1.el7.noarch
openstack-neutron-8.4.0-1.el7.noarch
openstack-neutron-openvswitch-8.4.0-1.el7.noarch
openstack-neutron-fwaas-8.4.0-1.el7.noarch

When installed finish the Openstack is fine.Sometime the OVS will going fail.
Partial log file from ovs-vswitched.log:

   2250  2017-10-16T09:19:00.318Z|12163|bridge|INFO|bridge br-int: added interface tap1839b0de-48 on port 1056

   2251 2017-10-16T09:19:00.622Z|12164|netdev_linux|INFO|ioctl(SIOCGIFHWADDR) on tap1839b0de-48 device failed: No such device

   2252 2017-10-16T09:19:01.738Z|12165|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2253 2017-10-16T09:19:01.753Z|12166|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2254 2017-10-16T09:19:01.769Z|12167|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2255 2017-10-16T09:19:01.784Z|12168|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2256 2017-10-16T09:19:01.797Z|12169|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2257 2017-10-16T09:19:02.662Z|12170|bridge|INFO|bridge br-int: added interface tap95a163a1-f7 on port 1057

   2258 2017-10-16T09:19:02.965Z|12171|netdev_linux|INFO|ioctl(SIOCGIFHWADDR) on tap95a163a1-f7 device failed: No such device

   2259 2017-10-16T09:19:04.317Z|12172|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2260 2017-10-16T09:19:04.330Z|12173|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2261 2017-10-16T09:19:04.345Z|12174|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2262 2017-10-16T09:19:04.359Z|12175|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2263 2017-10-16T09:19:04.375Z|12176|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2264 2017-10-16T09:19:05.285Z|12177|bridge|INFO|bridge br-int: added interface tap413a5f1b-79 on port 1058

   2265 2017-10-16T09:19:05.601Z|12178|netdev_linux|INFO|ioctl(SIOCGIFHWADDR) on tap413a5f1b-79 device failed: No such device

   2266 2017-10-16T09:19:05.605Z|12179|netdev_linux|WARN|Dropped 9 log messages in last 12 seconds (most recently, 2 seconds ago) due to excessive rate

   2267 2017-10-16T09:19:05.605Z|12180|netdev_linux|WARN|ioctl(SIOCGIFINDEX) on tap413a5f1b-79 device failed: No such device

   2268 2017-10-16T09:19:07.817Z|12181|netlink_socket|ERR|fcntl: Too many open files

   2269 2017-10-16T09:19:07.817Z|12182|dpif|WARN|system@ovs-system: failed to add tap50aa4927-e8 as port: Too many open files

   2270 2017-10-16T09:19:07.919Z|12183|netlink_socket|ERR|fcntl: Too many open files

   2271 2017-10-16T09:19:07.919Z|12184|dpif|WARN|system@ovs-system: failed to add tap50aa4927-e8 as port: Too many open files

   2272 2017-10-16T09:19:08.055Z|12185|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2273 2017-10-16T09:19:08.070Z|12186|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2274 2017-10-16T09:19:08.085Z|12187|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2275 2017-10-16T09:19:08.098Z|12188|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2276 2017-10-16T09:19:08.112Z|12189|connmgr|INFO|br-int<->unix: 1 flow_mods in the last 0 s (1 deletes)

   2277 2017-10-16T09:19:08.153Z|12190|netlink_socket|ERR|fcntl: Too many open files

   2278 2017-10-16T09:19:08.154Z|12191|dpif|WARN|system@ovs-system: failed to add tap50aa4927-e8 as port: Too many open files

   2279 2017-10-16T09:19:08.989Z|12192|netlink_socket|ERR|fcntl: Too many open files

   2280 2017-10-16T09:19:08.989Z|12193|dpif|WARN|system@ovs-system: failed to add tap64de99f1-2d as port: Too many open files

More info see my attachment.
Hope this helps some,
Thanks.