openstack/nova
Code Issues Proposed changes

Add new configuration option to turn postcopy on/off

Browse Source 
Since QEMU 2.5 and Libvirt 1.3.3 it is possible to use postcopy
live migration to ensure an upper limit in the amount of memory
to be transferred duing the live migration process. This option
enables to live migrate instances with memory-intensive workloads
by driving the migration process by the destination host, i.e.,
after the switch to postcopy mode, the destination VM is the active
one and therefore any dirty pages are directly generated at the
destination hosts.

Partially-implements: blueprint auto-live-migration-completion

Change-Id: I35b8400604eece5ddfba3e35015bcd3500d9f605
Signed-off-by: Luis Tomas <luis5tb@gmail.com>
Co-Authored-By: Pawel Koniszewski <pawel.koniszewski@intel.com>
This commit is contained in:
Luis Tomas
2016-06-13 16:42:11 +02:00
committed by Pawel Koniszewski
parent e1e68eb557
commit 3d83c462bc
5 changed files with 125 additions and 0 deletions
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20
nova/conf/libvirt.py
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@ -152,6 +152,26 @@ libvirt_general_opts = [
help='Time to wait, in seconds, for migration to make forward '
'progress in transferring data before aborting the '
'operation. Set to 0 to disable timeouts.'),
cfg.BoolOpt('live_migration_permit_post_copy',
default=False,
help="""
This option allows nova to switch an on-going live migration to post-copy
mode, i.e., switch the active VM to the one on the destination node before the
migration is complete, therefore ensuring an upper bound on the memory that
needs to be transferred. Post-copy requires libvirt>=1.3.3 and QEMU>=2.5.0.
When permitted, post-copy mode will be automatically activated if a
live-migration memory copy iteration does not make percentage increase of at
least 10% over the last iteration.
The live-migration force complete API also uses post-copy when permitted. If
post-copy mode is not available, force complete falls back to pausing the VM
to ensure the live-migration operation will complete.
When using post-copy mode, if the source and destination hosts loose network
connectivity, the VM being live-migrated will need to be rebooted. For more
details, please see the Administration guide.
"""),
cfg.StrOpt('snapshot_image_format',
choices=('raw', 'qcow2', 'vmdk', 'vdi'),
help='Snapshot image format. Defaults to same as source image'),

1
nova/tests/unit/virt/libvirt/fakelibvirt.py
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@ -94,6 +94,7 @@ VIR_MIGRATE_TUNNELLED = 4
VIR_MIGRATE_PERSIST_DEST = 8
VIR_MIGRATE_UNDEFINE_SOURCE = 16
VIR_MIGRATE_NON_SHARED_INC = 128
VIR_MIGRATE_POSTCOPY = 32768
VIR_NODE_CPU_STATS_ALL_CPUS = -1

69
nova/tests/unit/virt/libvirt/test_driver.py
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@ -1181,6 +1181,75 @@ class LibvirtConnTestCase(test.NoDBTestCase):
msg = mock_log.warning.call_args_list[1]
self.assertIn('contains the VIR_MIGRATE_TUNNELLED flag', msg[0][0])
@mock.patch.object(host.Host, 'has_min_version', return_value=True)
def test_live_migration_permit_postcopy_true(self, host):
self.flags(live_migration_permit_post_copy=True, group='libvirt')
self._do_test_parse_migration_flags(
lm_config=('VIR_MIGRATE_PERSIST_DEST, '
'VIR_MIGRATE_PEER2PEER, '
'VIR_MIGRATE_LIVE, '
'VIR_MIGRATE_TUNNELLED'),
bm_config=('VIR_MIGRATE_PERSIST_DEST, '
'VIR_MIGRATE_PEER2PEER, '
'VIR_MIGRATE_LIVE, '
'VIR_MIGRATE_TUNNELLED, '
'VIR_MIGRATE_NON_SHARED_INC'),
lm_expected=(libvirt_driver.libvirt.VIR_MIGRATE_UNDEFINE_SOURCE |
libvirt_driver.libvirt.VIR_MIGRATE_PEER2PEER |
libvirt_driver.libvirt.VIR_MIGRATE_LIVE |
libvirt_driver.libvirt.VIR_MIGRATE_TUNNELLED |
libvirt_driver.libvirt.VIR_MIGRATE_POSTCOPY),
bm_expected=(libvirt_driver.libvirt.VIR_MIGRATE_UNDEFINE_SOURCE |
libvirt_driver.libvirt.VIR_MIGRATE_PEER2PEER |
libvirt_driver.libvirt.VIR_MIGRATE_LIVE |
libvirt_driver.libvirt.VIR_MIGRATE_TUNNELLED |
libvirt_driver.libvirt.VIR_MIGRATE_NON_SHARED_INC |
libvirt_driver.libvirt.VIR_MIGRATE_POSTCOPY))
@mock.patch.object(host.Host, 'has_min_version', return_value=False)
def test_live_migration_permit_postcopy_true_old_libvirt(self, host):
self.flags(live_migration_permit_post_copy=True, group='libvirt')
self._do_test_parse_migration_flags(
lm_config=('VIR_MIGRATE_PERSIST_DEST, '
'VIR_MIGRATE_PEER2PEER, '
'VIR_MIGRATE_LIVE, '
'VIR_MIGRATE_TUNNELLED'),
bm_config=('VIR_MIGRATE_PERSIST_DEST, '
'VIR_MIGRATE_PEER2PEER, '
'VIR_MIGRATE_LIVE, '
'VIR_MIGRATE_TUNNELLED, '
'VIR_MIGRATE_NON_SHARED_INC'),
lm_expected=(libvirt_driver.libvirt.VIR_MIGRATE_UNDEFINE_SOURCE |
libvirt_driver.libvirt.VIR_MIGRATE_PEER2PEER |
libvirt_driver.libvirt.VIR_MIGRATE_LIVE |
libvirt_driver.libvirt.VIR_MIGRATE_TUNNELLED),
bm_expected=(libvirt_driver.libvirt.VIR_MIGRATE_UNDEFINE_SOURCE |
libvirt_driver.libvirt.VIR_MIGRATE_PEER2PEER |
libvirt_driver.libvirt.VIR_MIGRATE_LIVE |
libvirt_driver.libvirt.VIR_MIGRATE_TUNNELLED |
libvirt_driver.libvirt.VIR_MIGRATE_NON_SHARED_INC))
def test_live_migration_permit_postcopy_false(self):
self._do_test_parse_migration_flags(
lm_config=('VIR_MIGRATE_PERSIST_DEST, '
'VIR_MIGRATE_PEER2PEER, '
'VIR_MIGRATE_LIVE, '
'VIR_MIGRATE_TUNNELLED'),
bm_config=('VIR_MIGRATE_PERSIST_DEST, '
'VIR_MIGRATE_PEER2PEER, '
'VIR_MIGRATE_LIVE, '
'VIR_MIGRATE_TUNNELLED, '
'VIR_MIGRATE_NON_SHARED_INC'),
lm_expected=(libvirt_driver.libvirt.VIR_MIGRATE_UNDEFINE_SOURCE |
libvirt_driver.libvirt.VIR_MIGRATE_PEER2PEER |
libvirt_driver.libvirt.VIR_MIGRATE_LIVE |
libvirt_driver.libvirt.VIR_MIGRATE_TUNNELLED),
bm_expected=(libvirt_driver.libvirt.VIR_MIGRATE_UNDEFINE_SOURCE |
libvirt_driver.libvirt.VIR_MIGRATE_PEER2PEER |
libvirt_driver.libvirt.VIR_MIGRATE_LIVE |
libvirt_driver.libvirt.VIR_MIGRATE_TUNNELLED |
libvirt_driver.libvirt.VIR_MIGRATE_NON_SHARED_INC))
@mock.patch('nova.utils.get_image_from_system_metadata')
@mock.patch.object(host.Host,
'has_min_version', return_value=True)

29
nova/virt/libvirt/driver.py
View File

@ -284,6 +284,12 @@ ALLOWED_QEMU_SERIAL_PORTS = QEMU_MAX_SERIAL_PORTS - 1
# realtime support
MIN_LIBVIRT_REALTIME_VERSION = (1, 2, 13)
# libvirt postcopy support
MIN_LIBVIRT_POSTCOPY_VERSION = (1, 3, 3)
# qemu postcopy support
MIN_QEMU_POSTCOPY_VERSION = (2, 5, 0)
MIN_LIBVIRT_OTHER_ARCH = {arch.S390: MIN_LIBVIRT_KVM_S390_VERSION,
arch.S390X: MIN_LIBVIRT_KVM_S390_VERSION,
arch.PPC: MIN_LIBVIRT_KVM_PPC64_VERSION,
@ -587,6 +593,24 @@ class LibvirtDriver(driver.ComputeDriver):
return migration_flags
def _is_post_copy_available(self):
if self._host.has_min_version(lv_ver=MIN_LIBVIRT_POSTCOPY_VERSION,
hv_ver=MIN_QEMU_POSTCOPY_VERSION):
return True
return False
def _handle_live_migration_post_copy(self, migration_flags,
config_name):
if CONF.libvirt.live_migration_permit_post_copy:
if self._is_post_copy_available():
migration_flags |= libvirt.VIR_MIGRATE_POSTCOPY
else:
LOG.info(_LI('The live_migration_permit_post_copy is set '
'to True, but it is not supported.'))
elif self._is_post_copy_available():
migration_flags &= ~libvirt.VIR_MIGRATE_POSTCOPY
return migration_flags
def _parse_migration_flags(self):
def str2sum(str_val):
logical_sum = 0
@ -618,6 +642,11 @@ class LibvirtDriver(driver.ComputeDriver):
block_migration_flags = self._handle_live_migration_tunnelled(
block_migration_flags, block_config_name)
live_migration_flags = self._handle_live_migration_post_copy(
live_migration_flags, live_config_name)
block_migration_flags = self._handle_live_migration_post_copy(
block_migration_flags, block_config_name)
self._live_migration_flags = live_migration_flags
self._block_migration_flags = block_migration_flags

6
releasenotes/notes/automatic-live-migration-completion-post-copy-a7a3a986961c93d8.yaml Normal file
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@ -0,0 +1,6 @@
---
features:
- New configuration option live_migration_permit_post_copy
has been added to start live migrations in a way that allows
nova to switch an on-going live migration to post-copy mode.
Requires libvirt>=1.3.3 and QEMU>=2.5.0.