Merge "libvirt: Deprecate support for monitoring Intel CMT `perf` events"
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Zuul
Gerrit Code Review
commit
e4a2ebafe1
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@ -696,17 +696,29 @@ Possible cache modes:
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cfg.ListOpt('enabled_perf_events',
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default=[],
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help= """
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This is a performance event list which could be used as monitor. These events
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will be passed to libvirt domain xml while creating a new instances.
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Then event statistics data can be collected from libvirt. The minimum
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libvirt version is 2.0.0. For more information about `Performance monitoring
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events`, refer https://libvirt.org/formatdomain.html#elementsPerf .
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This will allow you to specify a list of events to monitor low-level
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performance of guests, and collect related statsitics via the libvirt
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driver, which in turn uses the Linux kernel's `perf` infrastructure.
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With this config attribute set, Nova will generate libvirt guest XML to
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monitor the specified events. For more information, refer to the
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"Performance monitoring events" section here:
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https://libvirt.org/formatdomain.html#elementsPerf. And here:
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https://libvirt.org/html/libvirt-libvirt-domain.html -- look for
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``VIR_PERF_PARAM_*``
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Possible values:
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* A string list. For example: ``enabled_perf_events = cmt, mbml, mbmt``
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The supported events list can be found in
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https://libvirt.org/html/libvirt-libvirt-domain.html ,
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which you may need to search key words ``VIR_PERF_PARAM_*``
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For example, to monitor the count of CPU cycles (total/elapsed) and the
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count of cache misses, enable them as follows::
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[libvirt]
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enabled_perf_events = cpu_clock, cache_misses
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Possible values: A string list. The list of supported events can be
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found here: https://libvirt.org/formatdomain.html#elementsPerf.
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Note that support for Intel CMT events (`cmt`, `mbmbt`, `mbml`) is
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deprecated, and will be removed in the "Stein" release. That's because
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the upstream Linux kernel (from 4.14 onwards) has deleted support for
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Intel CMT, because it is broken by design.
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"""),
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cfg.IntOpt('num_pcie_ports',
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default=0,
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@ -6567,34 +6567,6 @@ class LibvirtConnTestCase(test.NoDBTestCase,
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self.assertEqual(events, cfg.perf_events)
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@mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_CMT', True,
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create=True)
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@mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_MBMT', True,
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create=True)
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@mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_MBML', True,
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create=True)
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@mock.patch.object(host.Host, 'has_min_version', return_value=True)
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def test_get_guest_with_perf_supported(self,
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mock_min_version):
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self.flags(enabled_perf_events=['cmt', 'mbml', 'mbmt'],
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group='libvirt')
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caps = vconfig.LibvirtConfigCaps()
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caps.host = vconfig.LibvirtConfigCapsHost()
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caps.host.cpu = vconfig.LibvirtConfigCPU()
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caps.host.cpu.arch = fields.Architecture.X86_64
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caps.host.topology = fakelibvirt.NUMATopology()
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features = []
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for f in ('cmt', 'mbm_local', 'mbm_total'):
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feature = vconfig.LibvirtConfigGuestCPUFeature()
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feature.name = f
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feature.policy = fields.CPUFeaturePolicy.REQUIRE
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features.append(feature)
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caps.host.cpu.features = set(features)
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self._test_get_guest_with_perf(caps, ['cmt', 'mbml', 'mbmt'])
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@mock.patch.object(host.Host, 'has_min_version')
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def test_get_guest_with_perf_libvirt_unsupported(self, mock_min_version):
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@ -6627,6 +6599,46 @@ class LibvirtConnTestCase(test.NoDBTestCase,
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self._test_get_guest_with_perf(caps, [])
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@mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_CMT', True,
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create=True)
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@mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_MBMT', True,
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create=True)
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@mock.patch.object(fakelibvirt, 'VIR_PERF_PARAM_MBML', True,
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create=True)
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@mock.patch.object(libvirt_driver.LOG, 'warning')
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@mock.patch.object(host.Host, 'has_min_version', return_value=True)
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def test_intel_cmt_perf_deprecation_warning(self,
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mock_min_version,
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mock_warn):
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perf_events = ['cmt', 'mbml', 'mbmt']
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self.flags(enabled_perf_events=['cmt', 'mbml', 'mbmt'],
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group='libvirt')
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caps = vconfig.LibvirtConfigCaps()
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caps.host = vconfig.LibvirtConfigCapsHost()
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caps.host.cpu = vconfig.LibvirtConfigCPU()
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caps.host.cpu.arch = fields.Architecture.X86_64
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caps.host.topology = fakelibvirt.NUMATopology()
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features = []
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for f in ('cmt', 'mbm_local', 'mbm_total'):
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feature = vconfig.LibvirtConfigGuestCPUFeature()
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feature.name = f
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feature.policy = fields.CPUFeaturePolicy.REQUIRE
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features.append(feature)
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caps.host.cpu.features = set(features)
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self._test_get_guest_with_perf(caps, ['cmt', 'mbml', 'mbmt'])
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warning_count = 0
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call_args_list = mock_warn.call_args_list
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for call in call_args_list:
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# Call can be unpackaged as a tuple of args and kwargs
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# so we want to check the first arg in the args list
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if (len(call) == 2 and len(call[0]) == 2 and
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call[0][1] in perf_events and
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'Monitoring Intel CMT' in call[0][0]):
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warning_count += 1
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self.assertEqual(3, warning_count)
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def test_xml_and_uri_no_ramdisk_no_kernel(self):
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instance_data = dict(self.test_instance)
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self._check_xml_and_uri(instance_data,
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@ -4740,11 +4740,17 @@ class LibvirtDriver(driver.ComputeDriver):
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LOG.warning("Libvirt doesn't support event type %s.", event)
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return False
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if (event in PERF_EVENTS_CPU_FLAG_MAPPING
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and PERF_EVENTS_CPU_FLAG_MAPPING[event] not in cpu_features):
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LOG.warning("Host does not support event type %s.", event)
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return False
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if event in PERF_EVENTS_CPU_FLAG_MAPPING:
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LOG.warning('Monitoring Intel CMT `perf` event(s) %s is '
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'deprecated and will be removed in the "Stein" '
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'release. It was broken by design in the '
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'Linux kernel, so support for Intel CMT was '
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'removed from Linux 4.14 onwards. Therefore '
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'it is recommended to not enable them.',
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event)
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if PERF_EVENTS_CPU_FLAG_MAPPING[event] not in cpu_features:
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LOG.warning("Host does not support event type %s.", event)
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return False
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return True
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def _configure_guest_by_virt_type(self, guest, virt_type, caps, instance,
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@ -0,0 +1,17 @@
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---
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deprecations:
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- |
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Support to monitor performance events for Intel CMT (Cache
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Monitoring Technology, or "CQM" in Linux kernel parlance) -- namely
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``cmt``, ``mbm_local`` and ``mbm_total`` -- via the config attribute
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``[libvirt]/enabled_perf_events`` is now *deprecated* from Nova, and
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will be *removed* in the "Stein" release. Otherwise, if you have
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enabled those events, and upgraded to Linux kernel 4.14 (or suitable
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downstream version), it will result in instances failing to boot.
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That is because the Linux kernel has deleted the `perf` framework
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integration with Intel CMT, as the feature was broken by design --
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an incompatibility between Linux's `perf` infrastructure and Intel
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CMT. It was removed in upstream Linux version v4.14; but bear in
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mind that downstream Linux distributions with lower kernel versions
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than 4.14 have backported the said change.
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