Merge "libvirt: Enable autodeflate and freePageReporting for memballoon"

nova/tests/fixtures/libvirt_data.py

@@ -229,7 +229,7 @@ FAKE_KVM_GUEST = """
         <model type='virtio'/>
         <source bridge='virbr0'/>
       </interface>
-      <memballoon model='virtio'>
+      <memballoon model='virtio' autodeflate='on' freePageReporting='on'>
         <stats period='11'/>
       </memballoon>
       <input type="mouse" bus="virtio"/>

nova/tests/unit/virt/libvirt/test_config.py

@@ -4247,7 +4247,7 @@ class LibvirtConfigMemoryBalloonTest(LibvirtConfigBaseTest):
 
         xml = balloon.to_xml()
         expected_xml = """
-        <memballoon model='virtio'>
+        <memballoon model='virtio' autodeflate='on' freePageReporting='on'>
             <stats period='11'/>
         </memballoon>"""
 
@@ -4259,7 +4259,8 @@ class LibvirtConfigMemoryBalloonTest(LibvirtConfigBaseTest):
 
         xml = balloon.to_xml()
         expected_xml = """
-        <memballoon model='virtio' />"""
+        <memballoon model='virtio' autodeflate='on'
+                   freePageReporting='on' />"""
 
         self.assertXmlEqual(expected_xml, xml)
 
@@ -4272,7 +4273,7 @@ class LibvirtConfigMemoryBalloonTest(LibvirtConfigBaseTest):
 
         xml = balloon.to_xml()
         expected_xml = """
-            <memballoon model='virtio'>
+            <memballoon model='virtio' autodeflate='on' freePageReporting='on'>
               <driver iommu="on" />
             </memballoon>"""
 

nova/virt/libvirt/config.py

@@ -2302,6 +2302,8 @@ class LibvirtConfigMemoryBalloon(LibvirtConfigGuestDevice):
     def format_dom(self):
         dev = super(LibvirtConfigMemoryBalloon, self).format_dom()
         dev.set('model', str(self.model))
+        dev.set('autodeflate', 'on')
+        dev.set('freePageReporting', 'on')
         if self.period is not None:
             dev.append(etree.Element('stats', period=str(self.period)))
         if self.driver_iommu:

releasenotes/notes/libvirt-memballoon-autodeflate-freepage-reporting-13c25d410cca9d23.yaml

@@ -0,0 +1,11 @@
+---
+features:
+  - |
+    The libvirt driver now automatically enables ``autodeflate`` and
+    ``freePageReporting`` features for virtio memory balloon devices.
+    The ``autodeflate`` feature allows the QEMU virtio memory balloon
+    to release memory at the last moment before a guest process is
+    killed by the Out of Memory killer. The ``freePageReporting``
+    feature enables the memory balloon to return unused pages back
+    to the hypervisor for use by other guests or processes, improving
+    overall memory efficiency on the compute host.