openstack/nova
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Fix nits from change I676291ec0faa1dea0bd5050ef8e3426d171de4c6

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Change-Id: If6ea6701d73a4a8abb6a75c54308a386eec7a4b2
Implements: blueprint libvirt-file-backed-memory
This commit is contained in:
Zack Cornelius 2018-06-20 13:29:24 -05:00
parent 88213a0352
commit 8566dcfef4
9 changed files with 39 additions and 43 deletions
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36
doc/source/admin/file-backed-memory.rst
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@ -1,5 +1,5 @@
==================
File backed memory
File-backed memory
==================
.. important::
@ -7,7 +7,7 @@ File backed memory
As of the 18.0.0 Rocky release, the functionality described below is
only supported by the libvirt/KVM driver.
The file backed memory feature in Openstack allows a Nova node to serve guest
The file-backed memory feature in Openstack allows a Nova node to serve guest
memory from a file backing store. This mechanism uses the libvirt file memory
source, causing guest instance memory to be allocated as files within the
libvirt memory backing directory.
@ -17,48 +17,46 @@ this feature works best when used with very fast block devices or virtual file
systems - such as flash or RAM devices.
When configured, ``nova-compute`` will report the capacity configured for
file backed memory to placement in place of the total system memory capacity.
file-backed memory to placement in place of the total system memory capacity.
This allows the node to run more instances than would normally fit
within system memory.
To enable file backed memory, follow the steps below:
To enable file-backed memory, follow the steps below:
#. `Configure the backing store`_
#. `Configure Nova Compute for file backed memory`_
#. `Configure Nova Compute for file-backed memory`_
.. important::
It is not possible to live migrate from a node running a version of
OpenStack that does not support file backed memory to a node with file
OpenStack that does not support file-backed memory to a node with file
backed memory enabled. It is recommended that all Nova compute nodes are
upgraded to Rocky before enabling file backed memory.
upgraded to Rocky before enabling file-backed memory.
Prerequisites and Limitations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Libvirt
File backed memory requires libvirt version 4.0.0 or newer
File-backed memory requires libvirt version 4.0.0 or newer
Qemu
File backed memory requires qemu version 2.6.0 or newer
File-backed memory requires qemu version 2.6.0 or newer
Memory overcommit
File backed memory is not compatible with memory overcommit.
File-backed memory is not compatible with memory overcommit.
``ram_allocation_ratio`` must be set to ``1.0`` in ``nova.conf``, and the
host must not be added to a host aggregate with ``ram_allocation_ratio``
set to anything but ``1.0``.
Huge pages
File backed memory is not compatible with huge pages. Instances with huge
pages configured will not start on a host with file backed memory enabled. It
File-backed memory is not compatible with huge pages. Instances with huge
pages configured will not start on a host with file-backed memory enabled. It
is recommended to use host aggregates to ensure instances configured for
huge pages are not placed on hosts with file backed memory configured
huge pages are not placed on hosts with file-backed memory configured.
Handling these limitations could be optimized with a scheduler filter in the
future
future.
Configure the backing store
~~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -95,12 +93,12 @@ store mounted at (or above) this location.
# mount /dev/sdb /var/lib/libvirt/qemu/ram
Configure Nova Compute for file backed memory
Configure Nova Compute for file-backed memory
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#. Enable File backed memory in ``nova-compute``
#. Enable File-backed memory in ``nova-compute``
Configure Nova to utilize file backed memory with the capacity of the
Configure Nova to utilize file-backed memory with the capacity of the
backing store in MiB. 1048576 MiB (1 TiB) is used in this example.
Edit ``/etc/nova/nova.conf``

5
doc/source/admin/huge-pages.rst
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@ -56,8 +56,8 @@ Enabling huge pages on the host
-------------------------------
.. important::
Huge pages may not be used on a host configured for file backed memory. See
`File backed memory`_ for details
Huge pages may not be used on a host configured for file-backed memory. See
:doc:`file-backed-memory` for details
Persistent huge pages are required owing to their guaranteed availability.
However, persistent huge pages are not enabled by default in most environments.
@ -240,4 +240,3 @@ guide.
.. _`Linux THP guide`: https://www.kernel.org/doc/Documentation/vm/transhuge.txt
.. _`Linux hugetlbfs guide`: https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt
.. _`Image metadata`: https://docs.openstack.org/image-guide/image-metadata.html
.. _`File backed memory`: https://docs.openstack.org/nova/latest/admin/file-backed-memory.html

7
doc/source/user/support-matrix.ini
View File

@ -1476,6 +1476,7 @@ driver-impl-ironic=missing
driver-impl-libvirt-vz-vm=complete
driver-impl-libvirt-vz-ct=complete
driver-impl-powervm=missing
[operation.file-backed-memory]
title=File backed memory
status=optional
@ -1487,9 +1488,9 @@ notes=The file backed memory feature in Openstack allows a Nova node to serve
cli=
driver-impl-xenserver=missing
driver-impl-libvirt-kvm-x86=complete
driver-impl-libvirt-kvm-aarch64=complete
driver-impl-libvirt-kvm-ppc64=complete
driver-impl-libvirt-kvm-s390x=complete
driver-impl-libvirt-kvm-aarch64=unknown
driver-impl-libvirt-kvm-ppc64=unknown
driver-impl-libvirt-kvm-s390x=unknown
driver-impl-libvirt-qemu-x86=complete
driver-impl-libvirt-lxc=missing
driver-impl-libvirt-xen=missing

4
nova/conf/libvirt.py
View File

@ -747,9 +747,9 @@ Default value '0' moves calculating amount of ports to libvirt.
default=0,
min=0,
help="""
Available capacity in MiB for file backed memory.
Available capacity in MiB for file-backed memory.
Set to 0 to disable file backed memory.
Set to 0 to disable file-backed memory.
When enabled, instances will create memory files in the directory specified
in ``/etc/libvirt/qemu.conf``'s ``memory_backing_dir`` option. The default

2
nova/tests/unit/objects/test_migrate_data.py
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@ -239,7 +239,7 @@ class _TestLibvirtLiveMigrateData(object):
data = lambda x: x['nova_object.data']
primitive = data(obj.obj_to_primitive())
self.assertIn('serial_listen_addr', primitive)
self.assertIn('dst_wants_file_backed_memory', primitive)
primitive = data(obj.obj_to_primitive(target_version='1.0'))
self.assertNotIn('target_connect_addr', primitive)
self.assertNotIn('supported_perf_events', primitive)

10
nova/tests/unit/virt/libvirt/test_driver.py
View File

@ -1069,12 +1069,12 @@ class LibvirtConnTestCase(test.NoDBTestCase,
drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
drvr.init_host("dummyhost")
@mock.patch.object(
libvirt_driver.LibvirtDriver, "_check_file_backed_memory_support",)
def test_file_backed_memory_support_called(self, mock_file_backed_support):
def test_file_backed_memory_support_called(self):
drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
drvr.init_host("dummyhost")
self.assertTrue(mock_file_backed_support.called)
with mock.patch.object(drvr,
'_check_file_backed_memory_support') as mock_check_fb_support:
drvr.init_host("dummyhost")
self.assertTrue(mock_check_fb_support.called)
@mock.patch.object(fakelibvirt.Connection, 'getLibVersion',
return_value=versionutils.convert_version_to_int(

4
nova/tests/unit/virt/libvirt/test_host.py
View File

@ -676,9 +676,7 @@ class HostTestCase(test.NoDBTestCase):
self.assertEqual('one', self.host.get_memory_mb_total())
def test_get_memory_total_file_backed(self):
self.flags(file_backed_memory=1048576,
group="libvirt")
self.flags(file_backed_memory=1048576, group="libvirt")
self.assertEqual(1048576, self.host.get_memory_mb_total())
def test_get_memory_used(self):

8
nova/virt/libvirt/driver.py
View File

@ -607,8 +607,8 @@ class LibvirtDriver(driver.ComputeDriver):
'qemu': libvirt_utils.version_to_string(
MIN_QEMU_FILE_BACKED_VERSION)})
# file backed memory doesn't work with memory overcommit.
# Block service startup if file backed memory is enabled and
# file-backed memory doesn't work with memory overcommit.
# Block service startup if file-backed memory is enabled and
# ram_allocation_ratio is not 1.0
if CONF.ram_allocation_ratio != 1.0:
raise exception.InternalError(
@ -4713,7 +4713,7 @@ class LibvirtDriver(driver.ComputeDriver):
wantsfilebacked = CONF.libvirt.file_backed_memory > 0
if wantsmempages and wantsfilebacked:
# Can't use file backed memory with hugepages
# Can't use file-backed memory with hugepages
LOG.warning("Instance requested huge pages, but file-backed "
"memory is enabled, and incompatible with huge pages")
raise exception.MemoryPagesUnsupported()
@ -6552,7 +6552,7 @@ class LibvirtDriver(driver.ComputeDriver):
"""
# TODO(zcornelius): Remove this check in Stein, as we'll only support
# Rocky and newer computes.
# Rocky and newer computes.
# If file_backed_memory is enabled on this host, we have to make sure
# the source is new enough to support it. Since the source generates
# the XML for the destination, we depend on the source generating a

6
nova/virt/libvirt/migration.py
View File

@ -224,14 +224,14 @@ def _update_perf_events_xml(xml_doc, migrate_data):
def _update_memory_backing_xml(xml_doc, migrate_data):
"""Update libvirt domain XML for file backed memory
"""Update libvirt domain XML for file-backed memory
If incoming XML has a memoryBacking element, remove access, source,
and allocation children elements to get it to a known consistent state.
If no incoming memoryBacking element, create one.
If destination wants file backed memory, add source, access,
If destination wants file-backed memory, add source, access,
and allocation children.
"""
old_xml_has_memory_backing = True
@ -248,7 +248,7 @@ def _update_memory_backing_xml(xml_doc, migrate_data):
old_xml_has_memory_backing = False
else:
memory_backing = memory_backing[0]
# Remove existing file backed memory tags, if they exist.
# Remove existing file-backed memory tags, if they exist.
for name in ("access", "source", "allocation"):
tag = memory_backing.findall(name)
if tag: