openstack/nova
Code Issues Proposed changes

Add config option to configure TB cache size

Browse Source 
Qemu>=5.0.0 bumped the default tb-cache size to 1GiB(from 32MiB)
and this made it difficult to run multiple guest VMs on systems
running with lower memory. With Libvirt>=8.0.0 it's possible to
configure lower tb-cache size.

Below config option is introduced to allow configure
TB cache size as per environment needs, this only
applies to 'virt_type=qemu':-

[libvirt]tb_cache_size

Also enable this flag in nova-next job.

[1] https://github.com/qemu/qemu/commit/600e17b26
[2] https://gitlab.com/libvirt/libvirt/-/commit/58bf03f85

Closes-Bug: #1949606
Implements: blueprint libvirt-tb-cache-size
Change-Id: I49d2276ff3d3cc5d560a1bd96f13408e798b256a
This commit is contained in:
yatinkarel 2023-04-26 13:41:43 +00:00
parent f7ce4df51c
commit 3f7cc63d94
7 changed files with 121 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
.zuul.yaml
View File

@ -362,6 +362,9 @@
# machine type attaches more devices by default than pc
num_pcie_ports: 24
hw_machine_type: "x86_64=q35"
# Use lower TB cache than default(1GiB), only applicable with
# libvirt>=8.0.0
tb_cache_size: 128
compute:
# Switch off the provider association refresh, which should
# reduce the number of placement calls in steady state. Added in

16
nova/conf/libvirt.py
View File

@ -118,6 +118,7 @@ Related options:
* ``disk_prefix``: depends on this
* ``cpu_mode``: depends on this
* ``cpu_models``: depends on this
* ``tb_cache_size``: depends on this
"""),
cfg.StrOpt('connection_uri',
default='',
@ -900,6 +901,21 @@ Related options:
* :oslo.config:option:`libvirt.device_detach_attempts`
"""),
cfg.IntOpt('tb_cache_size',
min=0,
help="""
Qemu>=5.0.0 bumped the default tb-cache size to 1GiB(from 32MiB) and this
made it difficult to run multiple guest VMs on systems running with lower
memory. With Libvirt>=8.0.0 this config option can be used to configure
lower tb-cache size.
Set it to > 0 to configure tb-cache for guest VMs.
Related options:
* ``compute_driver`` (libvirt)
* ``virt_type`` (qemu)
"""),
]

8
nova/tests/unit/virt/libvirt/test_config.py
View File

@ -2414,6 +2414,14 @@ class LibvirtConfigGuestFeatureTest(LibvirtConfigBaseTest):
xml = obj.to_xml()
self.assertXmlEqual(xml, "<ioapic driver='libvirt'/>")
def test_feature_tcg(self):
obj = config.LibvirtConfigGuestFeatureTCG(10)
obj.driver = "libvirt"
xml = obj.to_xml()
self.assertXmlEqual(xml, '<tcg><tb-cache unit="MiB">10'
'</tb-cache></tcg>')
class LibvirtConfigGuestTest(LibvirtConfigBaseTest):

41
nova/tests/unit/virt/libvirt/test_driver.py
View File

@ -21367,6 +21367,47 @@ class LibvirtConnTestCase(test.NoDBTestCase,
cpu_model = drvr._get_cpu_model_mapping(expect_model[0])
self.assertEqual(cpu_model, expect_model[0])
@mock.patch.object(fakelibvirt.Connection, 'getLibVersion',
return_value=versionutils.convert_version_to_int(
libvirt_driver.MIN_LIBVIRT_TB_CACHE_SIZE) - 1)
def test_supports_tb_cache_size_fail(self, mock_getversion):
self.flags(virt_type='qemu', group='libvirt')
self.flags(tb_cache_size=10, group='libvirt')
driver = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
self.assertRaises(exception.InvalidConfiguration,
driver.init_host, 'dummyhost')
@mock.patch.object(libvirt_driver.LibvirtDriver,
'_register_all_undefined_instance_details',
new=mock.Mock())
@mock.patch.object(fakelibvirt.Connection, 'getLibVersion',
return_value=versionutils.convert_version_to_int(
libvirt_driver.MIN_LIBVIRT_TB_CACHE_SIZE))
def test_supports_tb_cache_size_ok(self, mock_getversion):
self.flags(virt_type='qemu', group='libvirt')
self.flags(tb_cache_size=10, group='libvirt')
driver = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
driver.init_host('dummyhost')
@mock.patch.object(fakelibvirt.Connection, 'getLibVersion',
return_value=versionutils.convert_version_to_int(
libvirt_driver.MIN_LIBVIRT_TB_CACHE_SIZE))
def test_get_guest_config_feature_tcg(self, mock_getversion):
self.flags(virt_type='qemu', group='libvirt')
self.flags(tb_cache_size=10, group='libvirt')
drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
instance_ref = objects.Instance(**self.test_instance)
image_meta = objects.ImageMeta.from_dict(self.test_image_meta)
disk_info = blockinfo.get_disk_info(
CONF.libvirt.virt_type, instance_ref, image_meta)
cfg = drvr._get_guest_config(
instance_ref, _fake_network_info(self), image_meta, disk_info)
expected = '<tcg><tb-cache unit="MiB">10</tb-cache></tcg>'
self.assertXmlEqual(expected, cfg.features[2].to_xml())
class TestGuestConfigSysinfoSerialOS(test.NoDBTestCase):
def setUp(self):

15
nova/virt/libvirt/config.py
View File

@ -2761,6 +2761,21 @@ class LibvirtConfigGuestFeatureSMM(LibvirtConfigGuestFeature):
return root
class LibvirtConfigGuestFeatureTCG(LibvirtConfigGuestFeature):
def __init__(self, cache_size, **kwargs):
super(LibvirtConfigGuestFeatureTCG, self).__init__("tcg", **kwargs)
self.cache_size = str(cache_size)
def format_dom(self):
root = super(LibvirtConfigGuestFeatureTCG, self).format_dom()
root.append(self._text_node("tb-cache", self.cache_size,
unit="MiB"))
return root
class LibvirtConfigGuestFeaturePMU(LibvirtConfigGuestFeature):
def __init__(self, state, **kwargs):

26
nova/virt/libvirt/driver.py
View File

@ -229,6 +229,8 @@ MIN_LIBVIRT_VIOMMU_VIRTIO_MODEL = (8, 3, 0)
MIN_LIBVIRT_AARCH64_CPU_COMPARE = (6, 9, 0)
MIN_LIBVIRT_TB_CACHE_SIZE = (8, 0, 0)
# Virtuozzo driver support
MIN_VIRTUOZZO_VERSION = (7, 0, 0)
@ -743,6 +745,9 @@ class LibvirtDriver(driver.ComputeDriver):
self._check_my_ip()
# TODO(ykarel) This can be dropped when MIN_LIBVIRT_VERSION>=8.0.0
self._supports_tb_cache_size()
if (CONF.libvirt.virt_type == 'lxc' and
not (CONF.libvirt.uid_maps and CONF.libvirt.gid_maps)):
LOG.warning("Running libvirt-lxc without user namespaces is "
@ -1217,6 +1222,19 @@ class LibvirtDriver(driver.ComputeDriver):
"cpu_shared_set' and '[compute] cpu_dedicated_set', "
"respectively, and undefine 'vcpu_pin_set'.")
def _supports_tb_cache_size(self):
if (
CONF.libvirt.virt_type == 'qemu' and
CONF.libvirt.tb_cache_size and
CONF.libvirt.tb_cache_size > 0
):
if not self._host.has_min_version(MIN_LIBVIRT_TB_CACHE_SIZE):
raise exception.InvalidConfiguration(
_("Nova requires libvirt version %s or greater "
"with '[libvirt] tb_cache_size' "
"configured.") %
libvirt_utils.version_to_string(MIN_LIBVIRT_TB_CACHE_SIZE))
def _prepare_migration_flags(self):
migration_flags = 0
@ -6176,6 +6194,14 @@ class LibvirtDriver(driver.ComputeDriver):
if not CONF.workarounds.libvirt_disable_apic:
guest.add_feature(vconfig.LibvirtConfigGuestFeatureAPIC())
if (
CONF.libvirt.virt_type == 'qemu' and
CONF.libvirt.tb_cache_size and
CONF.libvirt.tb_cache_size > 0
):
guest.add_feature(vconfig.LibvirtConfigGuestFeatureTCG(
CONF.libvirt.tb_cache_size))
if CONF.libvirt.virt_type in ('qemu', 'kvm') and os_type == 'windows':
hv = vconfig.LibvirtConfigGuestFeatureHyperV()
hv.relaxed = True

12
releasenotes/notes/libvirt-tb-cache-size-c0d0d672c0950393.yaml Normal file
View File

@ -0,0 +1,12 @@
---
features:
- |
Qemu>=5.0.0 bumped the default tb-cache size to 1GiB(from 32MiB) and this
made it difficult to run multiple guest VMs on systems running with lower
memory. With Libvirt>=8.0.0 it's possible to configure lower tb-cache
size. A new config option is introduced:
``[libvirt]tb_cache_size``
This config option can be used to configure tb_cache size
for guest VMs, it's only applicable with ``virt_type=qemu``.