Use new ``initial_xxx_allocation_ratio`` CONF

This patch adds new ``initial_xxx_allocation_ratio`` CONF options
and modifies the resource tracker's initial compute node creation to
use these values.

During the update_available_resource periodic task, the allocation
ratios reported to inventory for VCPU, MEMORY_MB and DISK_GB will
be based on:

* If CONF.*_allocation_ratio is set, use it. This overrides everything
  including externally set allocation ratios via the placement API.
* If reporting inventory for the first time, the
  CONF.initial_*_allocation_ratio value is used.
* For everything else, the inventory reported remains unchanged which
  allows operators to set the allocation ratios on the inventory records
  in placement directly without worrying about nova-compute overwriting
  those changes.

As a result, several TODOs are removed from the virt drivers that
implement the update_provider_tree interface and a TODO in the resource
tracker about unset-ing allocation ratios to get back to initial values.

Change-Id: I14a310b20bd9892e7b34464e6baad49bf5928ece
blueprint: initial-allocation-ratios

11 files changed, 309 insertions, 45 deletions

diff --git a/nova/compute/resource_tracker.py b/nova/compute/resource_tracker.py
index 5c21f60a6b..7d7ddc3be8 100644
--- a/nova/compute/resource_tracker.py
+++ b/nova/compute/resource_tracker.py
@@ -583,7 +583,7 @@ class ResourceTracker(object):
         # to be initialized with resource values.
         cn = objects.ComputeNode(context)
         cn.host = self.host
-        self._copy_resources(cn, resources)
+        self._copy_resources(cn, resources, initial=True)
         self.compute_nodes[nodename] = cn
         cn.create()
         LOG.info('Compute node record created for '
@@ -605,7 +605,7 @@ class ResourceTracker(object):
             dev_pools_obj = self.pci_tracker.stats.to_device_pools_obj()
             compute_node.pci_device_pools = dev_pools_obj
 
-    def _copy_resources(self, compute_node, resources):
+    def _copy_resources(self, compute_node, resources, initial=False):
         """Copy resource values to supplied compute_node."""
         nodename = resources['hypervisor_hostname']
         stats = self.stats[nodename]
@@ -629,20 +629,17 @@ class ResourceTracker(object):
         # resetting the ComputeNode fields to None because that will make
         # the _resource_change method think something changed when really it
         # didn't.
-        # TODO(mriedem): Will this break any scenarios where an operator is
-        # trying to *reset* the allocation ratios by changing config from
-        # non-None back to None? Maybe we should only do this if the fields on
-        # the ComputeNode object are not already set. For example, let's say
-        # the cpu_allocation_ratio config was 1.0 and then the operator wants
-        # to get back to the default (16.0 via the facade), and to do that they
-        # change the config back to None (or just unset the config option).
-        # Should we support that or treat these config options as "sticky" in
-        # that once you start setting them, you can't go back to the implied
-        # defaults by unsetting or resetting to None? Sort of like how
-        # per-tenant quota is sticky once you change it in the API.
+        # NOTE(yikun): The CONF.initial_(cpu|ram|disk)_allocation_ratio would
+        # be used when we initialize the compute node object, that means the
+        # ComputeNode.(cpu|ram|disk)_allocation_ratio will be set to
+        # CONF.initial_(cpu|ram|disk)_allocation_ratio when initial flag is
+        # True.
         for res in ('cpu', 'disk', 'ram'):
             attr = '%s_allocation_ratio' % res
-            conf_alloc_ratio = getattr(self, attr)
+            if initial:
+                conf_alloc_ratio = getattr(CONF, 'initial_%s' % attr)
+            else:
+                conf_alloc_ratio = getattr(self, attr)
             # NOTE(yikun): In Stein version, we change the default value of
             # (cpu|ram|disk)_allocation_ratio from 0.0 to None, but we still
             # should allow 0.0 to keep compatibility, and this 0.0 condition
diff --git a/nova/conf/compute.py b/nova/conf/compute.py
index 1258f82e08..1fe1d97168 100644
--- a/nova/conf/compute.py
+++ b/nova/conf/compute.py
@@ -399,11 +399,16 @@ NOTE: If this option is set to something *other than* ``None`` or ``0.0``, the
 allocation ratio will be overwritten by the value of this option, otherwise,
 the allocation ratio will not change. Once set to a non-default value, it is
 not possible to "unset" the config to get back to the default behavior. If you
-want to reset back to the default, explicitly specify 16.0.
+want to reset back to the initial value, explicitly specify it to the value of
+``initial_cpu_allocation_ratio``.
 
 Possible values:
 
 * Any valid positive integer or float value
+
+Related options:
+
+* ``initial_cpu_allocation_ratio``
 """),
     cfg.FloatOpt('ram_allocation_ratio',
         default=None,
@@ -425,11 +430,16 @@ NOTE: If this option is set to something *other than* ``None`` or ``0.0``, the
 allocation ratio will be overwritten by the value of this option, otherwise,
 the allocation ratio will not change. Once set to a non-default value, it is
 not possible to "unset" the config to get back to the default behavior. If you
-want to reset back to the default, explicitly specify 1.5.
+want to reset back to the initial value, explicitly specify it to the value of
+``initial_ram_allocation_ratio``.
 
 Possible values:
 
 * Any valid positive integer or float value
+
+Related options:
+
+* ``initial_ram_allocation_ratio``
 """),
     cfg.FloatOpt('disk_allocation_ratio',
         default=None,
@@ -455,11 +465,58 @@ NOTE: If this option is set to something *other than* ``None`` or ``0.0``, the
 allocation ratio will be overwritten by the value of this option, otherwise,
 the allocation ratio will not change. Once set to a non-default value, it is
 not possible to "unset" the config to get back to the default behavior. If you
-want to reset back to the default, explicitly specify 1.0.
+want to reset back to the initial value, explicitly specify it to the value of
+``initial_disk_allocation_ratio``.
 
 Possible values:
 
 * Any valid positive integer or float value
+
+Related options:
+
+* ``initial_disk_allocation_ratio``
+"""),
+    cfg.FloatOpt('initial_cpu_allocation_ratio',
+                 default=16.0,
+                 min=0.0,
+                 help="""
+This option helps you specify initial virtual CPU to physical CPU allocation
+ratio.
+
+This is only used when initially creating the ``computes_nodes`` table record
+for a given nova-compute service.
+
+Related options:
+
+* ``cpu_allocation_ratio``
+"""),
+    cfg.FloatOpt('initial_ram_allocation_ratio',
+                 default=1.5,
+                 min=0.0,
+                 help="""
+This option helps you specify initial virtual RAM to physical RAM allocation
+ratio.
+
+This is only used when initially creating the ``computes_nodes`` table record
+for a given nova-compute service.
+
+Related options:
+
+* ``ram_allocation_ratio``
+"""),
+    cfg.FloatOpt('initial_disk_allocation_ratio',
+                 default=1.0,
+                 min=0.0,
+                 help="""
+This option helps you specify initial virtual disk to physical disk allocation
+ratio.
+
+This is only used when initially creating the ``computes_nodes`` table record
+for a given nova-compute service.
+
+Related options:
+
+* ``disk_allocation_ratio``
 """)
 ]
 
diff --git a/nova/tests/functional/compute/test_resource_tracker.py b/nova/tests/functional/compute/test_resource_tracker.py
index c4ef50d743..0cb7b8280b 100644
--- a/nova/tests/functional/compute/test_resource_tracker.py
+++ b/nova/tests/functional/compute/test_resource_tracker.py
@@ -362,3 +362,107 @@ class TestUpdateComputeNodeReservedAndAllocationRatio(
 
         # The reserved host values should also come from config.
         self._assert_reserved_inventory(inventories)
+
+    def test_allocation_ratio_create_with_initial_allocation_ratio(self):
+        # The xxx_allocation_ratio is set to None by default, and we use
+        # 16.1/1.6/1.1 since disk_allocation_ratio defaults to 16.0/1.5/1.0.
+        self.flags(initial_cpu_allocation_ratio=16.1)
+        self.flags(initial_ram_allocation_ratio=1.6)
+        self.flags(initial_disk_allocation_ratio=1.1)
+        # Start a compute service which should create a corresponding resource
+        # provider in the placement service.
+        self._start_compute('fake-host')
+        # Assert the compute node resource provider exists in placement with
+        # the default reserved and allocation ratio values from config.
+        rp_uuid = self._get_provider_uuid_by_host('fake-host')
+        inventories = self._get_provider_inventory(rp_uuid)
+        ctxt = context.get_admin_context()
+        # Note that the CellDatabases fixture usage means we don't need to
+        # target the context to cell1 even though the compute_nodes table is
+        # in the cell1 database.
+        cn = objects.ComputeNode.get_by_uuid(ctxt, rp_uuid)
+        ratios = {
+            'VCPU': cn.cpu_allocation_ratio,
+            'MEMORY_MB': cn.ram_allocation_ratio,
+            'DISK_GB': cn.disk_allocation_ratio
+        }
+        initial_ratio_conf = {
+            'VCPU': CONF.initial_cpu_allocation_ratio,
+            'MEMORY_MB': CONF.initial_ram_allocation_ratio,
+            'DISK_GB': CONF.initial_disk_allocation_ratio
+        }
+        for rc, ratio in ratios.items():
+            self.assertIn(rc, inventories)
+            self.assertIn('allocation_ratio', inventories[rc])
+            # Check the allocation_ratio values come from the new
+            # CONF.initial_xxx_allocation_ratio
+            self.assertEqual(initial_ratio_conf[rc], ratio,
+                             'Unexpected allocation ratio for %s' % rc)
+            # Check the initial allocation ratio is updated to inventories
+            self.assertEqual(ratio, inventories[rc]['allocation_ratio'],
+                             'Unexpected allocation ratio for %s' % rc)
+
+    def test_allocation_ratio_overwritten_from_config(self):
+        # NOTE(yikun): This test case includes below step:
+        # 1. Overwrite the allocation_ratio via the placement API directly -
+        #    run the RT.update_available_resource periodic and assert the
+        #    allocation ratios are not overwritten from config.
+        #
+        # 2. Set the CONF.*_allocation_ratio, run the periodic, and assert
+        #    that the config overwrites what was set via the placement API.
+        compute_service = self._start_compute('fake-host')
+        rp_uuid = self._get_provider_uuid_by_host('fake-host')
+        ctxt = context.get_admin_context()
+
+        rt = compute_service.manager._get_resource_tracker()
+
+        inv = self.placement_api.get(
+            '/resource_providers/%s/inventories' % rp_uuid).body
+        ratios = {'VCPU': 16.1, 'MEMORY_MB': 1.6, 'DISK_GB': 1.1}
+
+        for rc, ratio in ratios.items():
+            inv['inventories'][rc]['allocation_ratio'] = ratio
+
+        # Overwrite the allocation_ratio via the placement API directly
+        self._update_inventory(rp_uuid, inv)
+        inv = self._get_provider_inventory(rp_uuid)
+        # Check inventories is updated to ratios
+        for rc, ratio in ratios.items():
+            self.assertIn(rc, inv)
+            self.assertIn('allocation_ratio', inv[rc])
+            self.assertEqual(ratio, inv[rc]['allocation_ratio'],
+                             'Unexpected allocation ratio for %s' % rc)
+
+        # Make sure xxx_allocation_ratio is None by default
+        self.assertIsNone(CONF.cpu_allocation_ratio)
+        self.assertIsNone(CONF.ram_allocation_ratio)
+        self.assertIsNone(CONF.disk_allocation_ratio)
+        # run the RT.update_available_resource periodic
+        rt.update_available_resource(ctxt, 'fake-host')
+        # assert the allocation ratios are not overwritten from config
+        inv = self._get_provider_inventory(rp_uuid)
+        for rc, ratio in ratios.items():
+            self.assertIn(rc, inv)
+            self.assertIn('allocation_ratio', inv[rc])
+            self.assertEqual(ratio, inv[rc]['allocation_ratio'],
+                             'Unexpected allocation ratio for %s' % rc)
+
+        # set the CONF.*_allocation_ratio
+        self.flags(cpu_allocation_ratio=15.9)
+        self.flags(ram_allocation_ratio=1.4)
+        self.flags(disk_allocation_ratio=0.9)
+
+        # run the RT.update_available_resource periodic
+        rt.update_available_resource(ctxt, 'fake-host')
+        inv = self._get_provider_inventory(rp_uuid)
+        ratios = {
+            'VCPU': CONF.cpu_allocation_ratio,
+            'MEMORY_MB': CONF.ram_allocation_ratio,
+            'DISK_GB': CONF.disk_allocation_ratio
+        }
+        # assert that the config overwrites what was set via the placement API.
+        for rc, ratio in ratios.items():
+            self.assertIn(rc, inv)
+            self.assertIn('allocation_ratio', inv[rc])
+            self.assertEqual(ratio, inv[rc]['allocation_ratio'],
+                             'Unexpected allocation ratio for %s' % rc)
diff --git a/nova/tests/functional/integrated_helpers.py b/nova/tests/functional/integrated_helpers.py
index 333b3b014f..e5f02d23ee 100644
--- a/nova/tests/functional/integrated_helpers.py
+++ b/nova/tests/functional/integrated_helpers.py
@@ -488,6 +488,17 @@ class ProviderUsageBaseTestCase(test.TestCase, InstanceHelperMixin):
             url= ('/resource_providers/%s/inventories' % rp_uuid),
             version='1.15', body=inv_body).body
 
+    def _update_inventory(self, rp_uuid, inv_body):
+        """This will update the inventory for a given resource provider.
+
+        :param rp_uuid: UUID of the resource provider to update
+        :param inv_body: inventory to set on the provider
+        :returns: APIResponse object with the results
+        """
+        return self.placement_api.put(
+            url= ('/resource_providers/%s/inventories' % rp_uuid),
+            body=inv_body).body
+
     def _get_resource_provider_by_uuid(self, rp_uuid):
         return self.placement_api.get(
             '/resource_providers/%s' % rp_uuid, version='1.15').body
diff --git a/nova/tests/unit/compute/test_resource_tracker.py b/nova/tests/unit/compute/test_resource_tracker.py
index a4e4d0b5ab..08a88c7d4e 100644
--- a/nova/tests/unit/compute/test_resource_tracker.py
+++ b/nova/tests/unit/compute/test_resource_tracker.py
@@ -1238,9 +1238,9 @@ class TestInitComputeNode(BaseTestCase):
             # NOTE(sbauza): ResourceTracker adds host field
             host=_HOSTNAME,
             # NOTE(sbauza): ResourceTracker adds CONF allocation ratios
-            ram_allocation_ratio=1.0,
-            cpu_allocation_ratio=1.0,
-            disk_allocation_ratio=1.0,
+            ram_allocation_ratio=CONF.initial_ram_allocation_ratio,
+            cpu_allocation_ratio=CONF.initial_cpu_allocation_ratio,
+            disk_allocation_ratio=CONF.initial_disk_allocation_ratio,
             stats={'failed_builds': 0},
             pci_device_pools=objects.PciDevicePoolList(objects=[]),
             uuid=uuids.compute_node_uuid
diff --git a/nova/tests/unit/virt/powervm/test_driver.py b/nova/tests/unit/virt/powervm/test_driver.py
index 9f3cd9d8c7..08ae97b1e7 100644
--- a/nova/tests/unit/virt/powervm/test_driver.py
+++ b/nova/tests/unit/virt/powervm/test_driver.py
@@ -217,7 +217,7 @@ class TestPowerVMDriver(test.NoDBTestCase):
     def test_update_provider_tree_complex_ptree(self):
         # Overrides inventory already on the provider; leaves other providers
         # and aggregates/traits alone.
-        with self._update_provider_tree() as (ptree, _):
+        with self._update_provider_tree() as (ptree, exp_inv):
             ptree.update_inventory('compute_host', {
                 # these should get blown away
                 'VCPU': {
@@ -238,6 +238,11 @@ class TestPowerVMDriver(test.NoDBTestCase):
                                            'for': 'ssp'})
             ptree.update_aggregates('ssp', [uuids.ss_agg])
             ptree.new_child('sriov', 'compute_host', uuid=uuids.sriov)
+            # Since CONF.cpu_allocation_ratio is not set and this is not
+            # the initial upt call (so CONF.initial_cpu_allocation_ratio would
+            # be used), the existing allocation ratio value from the tree is
+            # used.
+            exp_inv['VCPU']['allocation_ratio'] = 1.0
 
         # Make sure the compute's agg and traits were left alone
         cndata = ptree.data('compute_host')
diff --git a/nova/tests/unit/virt/test_virt_drivers.py b/nova/tests/unit/virt/test_virt_drivers.py
index d03370909e..f275250e0f 100644
--- a/nova/tests/unit/virt/test_virt_drivers.py
+++ b/nova/tests/unit/virt/test_virt_drivers.py
@@ -28,10 +28,12 @@ from oslo_utils import timeutils
 import six
 
 from nova.compute import manager
+from nova import conf
 from nova.console import type as ctype
 from nova import context
 from nova import exception
 from nova import objects
+from nova import rc_fields
 from nova import test
 from nova.tests import fixtures as nova_fixtures
 from nova.tests.unit import fake_block_device
@@ -46,6 +48,7 @@ from nova.virt import libvirt
 from nova.virt.libvirt import imagebackend
 
 LOG = logging.getLogger(__name__)
+CONF = conf.CONF
 
 
 def catch_notimplementederror(f):
@@ -809,6 +812,53 @@ class _VirtDriverTestCase(_FakeDriverBackendTestCase):
         self.assertEqual(instance.host,
             self.connection.network_binding_host_id(self.ctxt, instance))
 
+    def test_get_allocation_ratio(self):
+        inv = {}
+        self.flags(cpu_allocation_ratio=16.1)
+        self.flags(ram_allocation_ratio=1.6)
+        self.flags(disk_allocation_ratio=1.1)
+        expeced_ratios = {
+            rc_fields.ResourceClass.VCPU: CONF.cpu_allocation_ratio,
+            rc_fields.ResourceClass.MEMORY_MB: CONF.ram_allocation_ratio,
+            rc_fields.ResourceClass.DISK_GB: CONF.disk_allocation_ratio
+        }
+        # If conf is set, return conf
+        self.assertEqual(expeced_ratios,
+                         self.connection._get_allocation_ratios(inv))
+
+        self.flags(cpu_allocation_ratio=None)
+        self.flags(ram_allocation_ratio=None)
+        self.flags(disk_allocation_ratio=None)
+        self.flags(initial_cpu_allocation_ratio=15.9)
+        self.flags(initial_ram_allocation_ratio=1.4)
+        self.flags(initial_disk_allocation_ratio=0.9)
+        expeced_ratios = {
+            rc_fields.ResourceClass.VCPU:
+                CONF.initial_cpu_allocation_ratio,
+            rc_fields.ResourceClass.MEMORY_MB:
+                CONF.initial_ram_allocation_ratio,
+            rc_fields.ResourceClass.DISK_GB:
+                CONF.initial_disk_allocation_ratio
+        }
+        # if conf is unset and inv doesn't exists, return init conf
+        self.assertEqual(expeced_ratios,
+                         self.connection._get_allocation_ratios(inv))
+
+        inv = {rc_fields.ResourceClass.VCPU: {'allocation_ratio': 3.0},
+               rc_fields.ResourceClass.MEMORY_MB: {'allocation_ratio': 3.1},
+               rc_fields.ResourceClass.DISK_GB: {'allocation_ratio': 3.2}}
+        expeced_ratios = {
+            rc_fields.ResourceClass.VCPU:
+                inv[rc_fields.ResourceClass.VCPU]['allocation_ratio'],
+            rc_fields.ResourceClass.MEMORY_MB:
+                inv[rc_fields.ResourceClass.MEMORY_MB]['allocation_ratio'],
+            rc_fields.ResourceClass.DISK_GB:
+                inv[rc_fields.ResourceClass.DISK_GB]['allocation_ratio']
+        }
+        # if conf is unset and inv exists, return inv
+        self.assertEqual(expeced_ratios,
+                         self.connection._get_allocation_ratios(inv))
+
 
 class AbstractDriverTestCase(_VirtDriverTestCase, test.TestCase):
     def setUp(self):
diff --git a/nova/virt/driver.py b/nova/virt/driver.py
index 59340cbdaf..1fd33b0748 100644
--- a/nova/virt/driver.py
+++ b/nova/virt/driver.py
@@ -28,6 +28,7 @@ import six
 
 import nova.conf
 from nova.i18n import _
+from nova import rc_fields
 from nova.virt import event as virtevent
 
 CONF = nova.conf.CONF
@@ -862,6 +863,41 @@ class ComputeDriver(object):
         import nova.compute.utils as compute_utils  # avoid circular import
         return compute_utils.convert_mb_to_ceil_gb(CONF.reserved_host_disk_mb)
 
+    @staticmethod
+    def _get_allocation_ratios(inventory):
+        """Get the cpu/ram/disk allocation ratios for the given inventory.
+
+        This utility method is used to get the inventory allocation ratio
+        for VCPU, MEMORY_MB and DISK_GB resource classes based on the following
+        precedence:
+
+        * Use ``[DEFAULT]/*_allocation_ratio`` if set - this overrides
+          everything including externally set allocation ratios on the
+          inventory via the placement API
+        * Use ``[DEFAULT]/initial_*_allocation_ratio`` if a value does not
+          exist for a given resource class in the ``inventory`` dict
+        * Use what is already in the ``inventory`` dict for the allocation
+          ratio if the above conditions are false
+
+        :param inventory: dict, keyed by resource class, of inventory
+                          information.
+        :returns: Return a dict, keyed by resource class, of allocation ratio
+        """
+        keys = {'cpu': rc_fields.ResourceClass.VCPU,
+                'ram': rc_fields.ResourceClass.MEMORY_MB,
+                'disk': rc_fields.ResourceClass.DISK_GB}
+        result = {}
+        for res, rc in keys.items():
+            attr = '%s_allocation_ratio' % res
+            conf_ratio = getattr(CONF, attr)
+            if conf_ratio:
+                result[rc] = conf_ratio
+            elif rc not in inventory:
+                result[rc] = getattr(CONF, 'initial_%s' % attr)
+            else:
+                result[rc] = inventory[rc]['allocation_ratio']
+        return result
+
     def update_provider_tree(self, provider_tree, nodename, allocations=None):
         """Update a ProviderTree object with current resource provider and
         inventory information.
diff --git a/nova/virt/fake.py b/nova/virt/fake.py
index 26a06eabdb..b4e222217d 100644
--- a/nova/virt/fake.py
+++ b/nova/virt/fake.py
@@ -41,6 +41,7 @@ from nova import exception
 from nova.objects import diagnostics as diagnostics_obj
 from nova.objects import fields as obj_fields
 from nova.objects import migrate_data
+from nova import rc_fields
 from nova.virt import driver
 from nova.virt import hardware
 from nova.virt import virtapi
@@ -500,17 +501,19 @@ class FakeDriver(driver.ComputeDriver):
         return host_status
 
     def update_provider_tree(self, provider_tree, nodename, allocations=None):
-        # TODO(mriedem): The allocation_ratio config usage will change with
-        # blueprint initial-allocation-ratios. For now, the allocation ratio
-        # config values all default to 0.0 and the ComputeNode provides a
-        # facade for giving the real defaults, so we have to mimic that here.
+        # NOTE(yikun): If the inv record does not exists, the allocation_ratio
+        # will use the CONF.xxx_allocation_ratio value if xxx_allocation_ratio
+        # is set, and fallback to use the initial_xxx_allocation_ratio
+        # otherwise.
+        inv = provider_tree.data(nodename).inventory
+        ratios = self._get_allocation_ratios(inv)
         inventory = {
             'VCPU': {
                 'total': self.vcpus,
                 'min_unit': 1,
                 'max_unit': self.vcpus,
                 'step_size': 1,
-                'allocation_ratio': CONF.cpu_allocation_ratio or 16.0,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.VCPU],
                 'reserved': CONF.reserved_host_cpus,
             },
             'MEMORY_MB': {
@@ -518,7 +521,7 @@ class FakeDriver(driver.ComputeDriver):
                 'min_unit': 1,
                 'max_unit': self.memory_mb,
                 'step_size': 1,
-                'allocation_ratio': CONF.ram_allocation_ratio or 1.5,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.MEMORY_MB],
                 'reserved': CONF.reserved_host_memory_mb,
             },
             'DISK_GB': {
@@ -526,7 +529,7 @@ class FakeDriver(driver.ComputeDriver):
                 'min_unit': 1,
                 'max_unit': self.local_gb,
                 'step_size': 1,
-                'allocation_ratio': CONF.disk_allocation_ratio or 1.0,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.DISK_GB],
                 'reserved': self._get_reserved_host_disk_gb_from_config(),
             },
         }
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index 67fb6f53e5..276d33f4ac 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -6457,17 +6457,19 @@ class LibvirtDriver(driver.ComputeDriver):
         # TODO(sbauza): Use traits to make a better world.
         vgpus = self._get_vgpu_total()
 
-        # TODO(mriedem): The allocation_ratio config usage will change with
-        # blueprint initial-allocation-ratios. For now, the allocation ratio
-        # config values all default to 0.0 and the ComputeNode provides a
-        # facade for giving the real defaults, so we have to mimic that here.
+        # NOTE(yikun): If the inv record does not exists, the allocation_ratio
+        # will use the CONF.xxx_allocation_ratio value if xxx_allocation_ratio
+        # is set, and fallback to use the initial_xxx_allocation_ratio
+        # otherwise.
+        inv = provider_tree.data(nodename).inventory
+        ratios = self._get_allocation_ratios(inv)
         result = {
             rc_fields.ResourceClass.VCPU: {
                 'total': vcpus,
                 'min_unit': 1,
                 'max_unit': vcpus,
                 'step_size': 1,
-                'allocation_ratio': CONF.cpu_allocation_ratio or 16.0,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.VCPU],
                 'reserved': CONF.reserved_host_cpus,
             },
             rc_fields.ResourceClass.MEMORY_MB: {
@@ -6475,7 +6477,7 @@ class LibvirtDriver(driver.ComputeDriver):
                 'min_unit': 1,
                 'max_unit': memory_mb,
                 'step_size': 1,
-                'allocation_ratio': CONF.ram_allocation_ratio or 1.5,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.MEMORY_MB],
                 'reserved': CONF.reserved_host_memory_mb,
             },
         }
@@ -6492,7 +6494,7 @@ class LibvirtDriver(driver.ComputeDriver):
             'min_unit': 1,
             'max_unit': disk_gb,
             'step_size': 1,
-            'allocation_ratio': CONF.disk_allocation_ratio or 1.0,
+            'allocation_ratio': ratios[rc_fields.ResourceClass.DISK_GB],
             'reserved': self._get_reserved_host_disk_gb_from_config(),
         }
 
diff --git a/nova/virt/powervm/driver.py b/nova/virt/powervm/driver.py
index a153257ee7..21a6a979ab 100644
--- a/nova/virt/powervm/driver.py
+++ b/nova/virt/powervm/driver.py
@@ -191,35 +191,34 @@ class PowerVMDriver(driver.ComputeDriver):
         # update_available_resource flow.
         data = self._get_available_resource()
 
-        # TODO(efried): Fix these to reflect something like reality
-        # For now, duplicate the logic the resource tracker uses via
-        # update_compute_node when get_inventory/update_provider_tree is not
-        # implemented.
-        cpu_alloc_ratio = CONF.cpu_allocation_ratio or 16.0
+        # NOTE(yikun): If the inv record does not exists, the allocation_ratio
+        # will use the CONF.xxx_allocation_ratio value if xxx_allocation_ratio
+        # is set, and fallback to use the initial_xxx_allocation_ratio
+        # otherwise.
+        inv = provider_tree.data(nodename).inventory
+        ratios = self._get_allocation_ratios(inv)
         cpu_reserved = CONF.reserved_host_cpus
-        mem_alloc_ratio = CONF.ram_allocation_ratio or 1.5
         mem_reserved = CONF.reserved_host_memory_mb
-        disk_alloc_ratio = CONF.disk_allocation_ratio or 1.0
         disk_reserved = self._get_reserved_host_disk_gb_from_config()
 
         inventory = {
             rc_fields.ResourceClass.VCPU: {
                 'total': data['vcpus'],
                 'max_unit': data['vcpus'],
-                'allocation_ratio': cpu_alloc_ratio,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.VCPU],
                 'reserved': cpu_reserved,
             },
             rc_fields.ResourceClass.MEMORY_MB: {
                 'total': data['memory_mb'],
                 'max_unit': data['memory_mb'],
-                'allocation_ratio': mem_alloc_ratio,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.MEMORY_MB],
                 'reserved': mem_reserved,
             },
             rc_fields.ResourceClass.DISK_GB: {
                 # TODO(efried): Proper DISK_GB sharing when SSP driver in play
                 'total': int(data['local_gb']),
                 'max_unit': int(data['local_gb']),
-                'allocation_ratio': disk_alloc_ratio,
+                'allocation_ratio': ratios[rc_fields.ResourceClass.DISK_GB],
                 'reserved': disk_reserved,
             },
         }