Added a host_cpu_usable_by_vms config option

neat.conf

@@ -80,6 +80,10 @@ data_collector_data_length = 100
 # This is used for logging host overloads into the database.
 host_cpu_overload_threshold = 0.7
 
+# The threshold on the overall (all cores) utilization of the physical
+# CPU of a host that can be allocated to VMs.
+host_cpu_usable_by_vms = 0.75
+
 # The user name for connecting to the compute hosts to switch them
 # into the sleep mode
 compute_user = neat

neat/config.py

@@ -55,6 +55,7 @@ REQUIRED_FIELDS = [
     'data_collector_interval',
     'data_collector_data_length',
     'host_cpu_overload_threshold',
+    'host_cpu_usable_by_vms',
     'compute_user',
     'compute_password',
     'sleep_command',

neat/locals/manager.py

@@ -158,7 +158,7 @@ def init_state(config):
         log.critical(message)
         raise OSError(message)
 
-    physical_cpu_mhz_total = common.physical_cpu_mhz_total(vir_connection)
+    physical_cpu_mhz_total = int(common.physical_cpu_mhz_total(vir_connection))
     return {'previous_time': 0.,
             'vir_connection': vir_connection,
             'db': init_db(config['sql_connection']),
@@ -218,9 +218,10 @@ def execute(config, state):
             log.info('The host is idle')
         return state
 
-    physical_cpu_mhz_total = int(state['physical_cpu_mhz_total'])
+    physical_cpu_mhz_total = state['physical_cpu_mhz_total']
     host_cpu_utilization = vm_mhz_to_percentage(
-        vm_cpu_mhz, physical_cpu_mhz_total)
+        vm_cpu_mhz, 
+        physical_cpu_mhz_total * float(config['host_cpu_usable_by_vms']))
     time_step = int(config['data_collector_interval'])
     migration_time = common.calculate_migration_time(
         vm_ram, float(config['network_migration_bandwidth']))