Comment 7 for bug 1649124

It seems like this is happening:

  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
26257 root 10 -10 416308 52272 9268 D 141.4 0.3 27:16.77 ovs-vswitchd

And in journalctl:
Dec 14 00:10:03 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04989|netlink_socket|ERR|Dropped 32820 log messages in last 1 seconds (most recently, 0 seconds ago) due to excessive rate
Dec 14 00:10:03 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04990|netlink_socket|ERR|transaction error (Permission denied)
Dec 14 00:10:04 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04991|netlink_socket|ERR|Dropped 41365 log messages in last 1 seconds (most recently, 0 seconds ago) due to excessive rate
Dec 14 00:10:04 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04992|netlink_socket|ERR|transaction error (Permission denied)
Dec 14 00:10:05 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04993|netlink_socket|ERR|Dropped 39747 log messages in last 1 seconds (most recently, 0 seconds ago) due to excessive rate
Dec 14 00:10:05 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04994|netlink_socket|ERR|transaction error (Permission denied)
Dec 14 00:10:06 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04995|socket_util|ERR|Dropped 201303 log messages in last 12 seconds (most recently, 0 seconds ago) due to excessive rate
Dec 14 00:10:06 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04996|socket_util|ERR|getsockopt(SO_RCVBUF): Permission denied
Dec 14 00:10:06 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04997|netlink_socket|ERR|Dropped 30751 log messages in last 1 seconds (most recently, 0 seconds ago) due to excessive rate
Dec 14 00:10:06 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04998|netlink_socket|ERR|transaction error (Permission denied)
Dec 14 00:10:07 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|04999|netlink_socket|ERR|Dropped 49549 log messages in last 1 seconds (most recently, 0 seconds ago) due to excessive rate
Dec 14 00:10:07 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|05000|netlink_socket|ERR|transaction error (Permission denied)
Dec 14 00:10:08 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|05001|netlink_socket|ERR|Dropped 34087 log messages in last 1 seconds (most recently, 0 seconds ago) due to excessive rate
Dec 14 00:10:08 undercloud-0-trunk.localdomain ovs-vswitchd[26257]: ovs|05002|netlink_socket|ERR|transaction error (Permission denied)

I'm not sure if it's related yet.