Comment 4 for bug 1822268

As a potential workaround, the cloud operator can update the resource provider inventory database entries for allocation ratios like this:

# list each hypervisor and it's provider uuid
openstack resource provider list
# show current totals and allocation ratios for the given provider
openstack resource provider inventory list <provider uuid>
# update the allocation_ratio for VCPU, MEMORY_MB, or DISK_GB "class" for a given provider
openstack resource provider inventory class set --allocation_ratio $NEW_RATIO --total $CURRENT_TOTAL --max_unit $CURRENT_TOTAL <provider uuid> $CLASS

Unfortunately, --total must be updated while changing allocation_ratio for any class.

If you wanted to change RAM allocation_ratio across all hypervisors, for instance, you might use a loop such as:

new_ratio=0.9
resource_class=MEMORY_MB
reserved_size=512
for prov_uuid in $(openstack resource provider list -f value -c uuid); do
  current_total=$(openstack resource provider inventory show -f value -c total $prov_uuid $resource_class)
  openstack resource provider inventory class set --allocation_ratio $new_ratio --total $current_total --max_unit $current_total --reserved $reserved_size $prov_uuid $resource_class
done

This blueprint seems to suggest this may be reverted periodically, so use this workaround wisely and with caution.

https://specs.openstack.org/openstack/nova-specs/specs/stein/implemented/initial-allocation-ratios.html#manually-set-placement-allocation-ratios-are-overwritten