Comment 2 for bug 1684272

Likely cause:

April 17th updates job http://logs.openstack.org/50/454650/1/check-tripleo/gate-tripleo-ci-centos-7-ovb-updates/e516b56/logs/postci.txt.gz:
ControllerServiceChain 37.0

Aprily 19th updates job http://logs.openstack.org/36/458036/2/check-tripleo/gate-tripleo-ci-centos-7-ovb-updates/0a15c0f/logs/postci.txt.gz:
ControllerServiceChain 547.0

That's a huge increase that approximately corresponds to the increase in stack update time.