Remove hugepage fstab entry and use qemu-kvm init

The hugepages fstab entry can stop systems from booting if the
/run filesystem is not available. The qemu-kvm init script can
be used to enable hugepages by setting KVM_HUGEPAGES=1

This apporach works for both upstart and systemd (where the old
System V script is used). However, for a systemd system the
prefered approach would be to enable hugepages via kernel
parameters set in MAAS.

Change-Id: Ib91ca930a91da3d75dbd96f7d55e7e259cb50fd1
Closes-Bug: 1518771

config.yaml

@@ -257,6 +257,9 @@ options:
     description: |
       The pecentage of system memory to use for hugepages eg '10%' or the total
       number of 2M hugepages - eg "1024".
+      For a systemd system (wily and later) the prefered approach is to enable
+      hugepages via kernel parameters set in MAAS and systemd will mount them
+      automatically.
   action-managed-upgrade:
     type: boolean
     default: False

hooks/nova_compute_context.py

@@ -136,6 +136,9 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
 
         if config('hugepages'):
             ctxt['hugepages'] = True
+            ctxt['kvm_hugepages'] = 1
+        else:
+            ctxt['kvm_hugepages'] = 0
 
         db = kv()
         if db.get('host_uuid'):

hooks/nova_compute_utils.py

@@ -17,6 +17,7 @@ from charmhelpers.fetch import (
     apt_install,
 )
 
+from charmhelpers.core.fstab import Fstab
 from charmhelpers.core.host import (
     adduser,
     add_group,
@@ -65,7 +66,6 @@ from charmhelpers.contrib.python.packages import (
 
 from charmhelpers.core.hugepage import hugepage_support
 from charmhelpers.core.host import (
-    fstab_mount,
     rsync,
 )
 
@@ -158,6 +158,7 @@ LIBVIRTD_CONF = '/etc/libvirt/libvirtd.conf'
 LIBVIRT_BIN = '/etc/default/libvirt-bin'
 LIBVIRT_BIN_OVERRIDES = '/etc/init/libvirt-bin.override'
 NOVA_CONF = '%s/nova.conf' % NOVA_CONF_DIR
+QEMU_KVM = '/etc/default/qemu-kvm'
 
 BASE_RESOURCE_MAP = {
     NOVA_CONF: {
@@ -192,6 +193,10 @@ LIBVIRT_RESOURCE_MAP = {
         'services': ['libvirt-bin'],
         'contexts': [NovaComputeLibvirtContext()],
     },
+    QEMU_KVM: {
+        'services': ['qemu-kvm'],
+        'contexts': [NovaComputeLibvirtContext()],
+    },
     LIBVIRTD_CONF: {
         'services': ['libvirt-bin'],
         'contexts': [NovaComputeLibvirtContext()],
@@ -786,8 +791,10 @@ def install_hugepages():
             mount=False,
             set_shmmax=True,
         )
+        # Remove hugepages entry if present due to Bug #1518771
+        Fstab.remove_by_mountpoint(mnt_point)
         if subprocess.call(['mountpoint', mnt_point]):
-            fstab_mount(mnt_point)
+            service_restart('qemu-kvm')
         rsync(
             charm_dir() + '/files/qemu-hugefsdir',
             '/etc/init.d/qemu-hugefsdir'

templates/qemu-kvm

@@ -0,0 +1,6 @@
+###############################################################################
+# [ WARNING ]
+# Configuration file maintained by Juju. Local changes may be overwritten.
+###############################################################################
+KVM_HUGEPAGES={{ kvm_hugepages }}
+

unit_tests/test_nova_compute_contexts.py

@@ -184,6 +184,7 @@ class NovaComputeContextTests(CharmTestCase):
         self.assertEqual(
             {'libvirtd_opts': '-d',
              'arch': platform.machine(),
+             'kvm_hugepages': 0,
              'listen_tls': 0,
              'host_uuid': self.host_uuid}, libvirt())
 
@@ -195,6 +196,7 @@ class NovaComputeContextTests(CharmTestCase):
         self.assertEqual(
             {'libvirtd_opts': '-d -l',
              'arch': platform.machine(),
+             'kvm_hugepages': 0,
              'listen_tls': 0,
              'host_uuid': self.host_uuid}, libvirt())
 
@@ -207,6 +209,20 @@ class NovaComputeContextTests(CharmTestCase):
             {'libvirtd_opts': '-d',
              'disk_cachemodes': 'file=unsafe,block=none',
              'arch': platform.machine(),
+             'kvm_hugepages': 0,
+             'listen_tls': 0,
+             'host_uuid': self.host_uuid}, libvirt())
+
+    def test_libvirt_hugepages(self):
+        self.kv.return_value = FakeUnitdata(**{'host_uuid': self.host_uuid})
+        self.test_config.set('hugepages', '22')
+        libvirt = context.NovaComputeLibvirtContext()
+
+        self.assertEqual(
+            {'libvirtd_opts': '-d',
+             'arch': platform.machine(),
+             'hugepages': True,
+             'kvm_hugepages': 1,
              'listen_tls': 0,
              'host_uuid': self.host_uuid}, libvirt())
 

unit_tests/test_nova_compute_utils.py

@@ -31,7 +31,7 @@ TO_PATCH = [
     'charm_dir',
     'hugepage_support',
     'rsync',
-    'fstab_mount',
+    'Fstab',
 ]
 
 openstack_origin_git = \
@@ -613,7 +613,8 @@ class NovaComputeUtilsTests(CharmTestCase):
             call(['update-rc.d', 'qemu-hugefsdir', 'defaults']),
         ]
         _check_call.assert_has_calls(check_call_calls)
-        self.fstab_mount.assert_called_with('/run/hugepages/kvm')
+        self.Fstab.remove_by_mountpoint.assert_called_with(
+            '/run/hugepages/kvm')
 
     @patch('psutil.virtual_memory')
     @patch('subprocess.check_call')
@@ -631,16 +632,6 @@ class NovaComputeUtilsTests(CharmTestCase):
             set_shmmax=True,
         )
 
-    @patch('psutil.virtual_memory')
-    @patch('subprocess.check_call')
-    @patch('subprocess.call')
-    def test_install_hugepages_already_mounted(self, _call, _check_call,
-                                               _virt_mem):
-        self.test_config.set('hugepages', '2048')
-        _call.return_value = 0
-        utils.install_hugepages()
-        self.assertEqual(self.fstab_mount.call_args_list, [])
-
     def test_assess_status(self):
         with patch.object(utils, 'assess_status_func') as asf:
             callee = MagicMock()