Add knob for changing cpu_allocation_ratio and turn it on by default

config.yaml

@@ -170,4 +170,11 @@ options:
       The CPU multiplier to use when configuring worker processes for
       Nova and Neutron.  By default, the number of workers for each daemon
       is set to the number of CPU's a service unit has.
-
+  cpu-allocation-ratio:
+    type: float
+    default: 16.0
+    description: |
+      The per physical core -> virtual core ratio to use in the Nova scheduler.
+      .
+      Increasing this value will increase instance density on compute nodes
+      at the expense of instance performance.

hooks/nova_cc_context.py

@@ -213,3 +213,10 @@ class WorkerConfigContext(context.OSContextGenerator):
             "workers": psutil.NUM_CPUS * multiplier
         }
         return ctxt
+
+
+class NovaConfigContext(WorkerConfigContext):
+    def __call__(self):
+        ctxt = super(NovaConfigContext, self).__call__()
+        ctxt['cpu_allocation_ratio'] = config('cpu-allocation-ratio')
+        return ctxt

hooks/nova_cc_utils.py

@@ -103,14 +103,13 @@ BASE_RESOURCE_MAP = OrderedDict([
                      context.SubordinateConfigContext(
                          interface='nova-vmware',
                          service='nova',
-                         config_file=NOVA_CONF,
-                     ),
+                         config_file=NOVA_CONF),
                      context.SyslogContext(),
                      nova_cc_context.HAProxyContext(),
                      nova_cc_context.IdentityServiceContext(),
                      nova_cc_context.VolumeServiceContext(),
                      nova_cc_context.NeutronCCContext(),
-                     nova_cc_context.WorkerConfigContext()],
+                     nova_cc_context.NovaConfigContext()],
     }),
     (NOVA_API_PASTE, {
         'services': [s for s in BASE_SERVICES if 'api' in s],
@@ -151,7 +150,7 @@ BASE_RESOURCE_MAP = OrderedDict([
                      nova_cc_context.NeutronCCContext(),
                      nova_cc_context.HAProxyContext(),
                      context.SyslogContext(),
-                     nova_cc_context.WorkerConfigContext()],
+                     nova_cc_context.NovaConfigContext()],
     }),
     (NEUTRON_DEFAULT, {
         'services': ['neutron-server'],

templates/havana/nova.conf

@@ -20,6 +20,13 @@ volumes_path=/var/lib/nova/volumes
 enabled_apis=ec2,osapi_compute,metadata
 auth_strategy=keystone
 compute_driver=libvirt.LibvirtDriver
+
+osapi_compute_workers = {{ workers }}
+ec2_workers = {{ workers }}
+
+scheduler_default_filters = RetryFilter,AvailabilityZoneFilter,CoreFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter 
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+
 {% if keystone_ec2_url -%}
 keystone_ec2_url = {{ keystone_ec2_url }}
 {% endif -%}

templates/icehouse/nova.conf

@@ -1,3 +1,4 @@
+# icehouse
 ###############################################################################
 # [ WARNING ]
 # Configuration file maintained by Juju. Local changes may be overwritten.
@@ -24,6 +25,9 @@ compute_driver=libvirt.LibvirtDriver
 osapi_compute_workers = {{ workers }}
 ec2_workers = {{ workers }}
 
+scheduler_default_filters = RetryFilter,AvailabilityZoneFilter,CoreFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter 
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+
 {% if keystone_ec2_url -%}
 keystone_ec2_url = {{ keystone_ec2_url }}
 {% endif -%}