Comment 1 for bug 1804125

It's a regression with placement being used by the nova scheduler since Ocata. There is a related nova blueprint in the stein release:

https://specs.openstack.org/openstack/nova-specs/specs/stein/approved/initial-allocation-ratios.html

There is also this which builds on that blueprint but probably won't get done in stein since it's not being worked on: https://review.openstack.org/#/c/544683/

Here is a related ML thread about the regression:

http://lists.openstack.org/pipermail/openstack-dev/2018-January/126283.html