Re: [Xen-devel] [libvirt] libvirt/libxl implemetation of get_online_cpu / virNodeGetCPUMap?

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Tue, Feb 24, 2015 at 03:00:16PM +0000, Anthony PERARD wrote:
> On Tue, Feb 24, 2015 at 01:22:19PM +0000, Daniel P. Berrange wrote:
> > On Tue, Feb 24, 2015 at 01:15:57PM +0000, Anthony PERARD wrote:
> > > On Tue, Feb 24, 2015 at 12:46:44PM +0000, Daniel P. Berrange wrote:
> > > > On Tue, Feb 24, 2015 at 12:41:01PM +0000, Anthony PERARD wrote:
> > > > > Hi,
> > > > > 
> > > > > A recent OpenStack nova commit make use of virNodeGetCPUMap to get 
> > > > > the list
> > > > > of online cpu of a host. But this API is not implemented for the 
> > > > > libvirt
> > > > > xen driver.
> > > > > 
> > > > > The commit:
> > > > >   Add handling for offlined CPUs to the nova libvirt driver.
> > > > > https://review.openstack.org/gitweb?p=openstack/nova.git;a=commitdiff;h=0696a5cd5f0fdc08951a074961bb8ce0c3310086
> > > > 
> > > > FWIW, this should not impact Xen based on my understanding. The code
> > > > path in question should only be used when Nova is setup todo NUMA
> > > > pinning support, and that is not supported with Xen in OpenStack,
> > > > only KVM.  Did it actually cause failures for you, or are you simply
> > > > keeping track of all used APIs in Nova as a sanity check ?
> > > 
> > > It prevent nova from starting. I do the setup with DevStack.
> > > 
> > > The error:
> > > libvirtError: this function is not supported by the connection driver: 
> > > virNodeGetCPUMap
> > > 
> > > And a part of the traceback:
> > >   File "/opt/stack/nova/nova/openstack/common/service.py", line 491, in 
> > > run_service
> > >     service.start()
> > >   File "/opt/stack/nova/nova/service.py", line 181, in start
> > >     self.manager.pre_start_hook()
> > >   File "/opt/stack/nova/nova/compute/manager.py", line 1188, in 
> > > pre_start_hook
> > >     self.update_available_resource(nova.context.get_admin_context())
> > >   File "/opt/stack/nova/nova/compute/manager.py", line 6062, in 
> > > update_available_resource
> > >     rt.update_available_resource(context)
> > >   File "/opt/stack/nova/nova/compute/resource_tracker.py", line 315, in 
> > > update_available_resource
> > >     resources = self.driver.get_available_resource(self.nodename)
> > >   File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 4896, in 
> > > get_available_resource
> > >     numa_topology = self._get_host_numa_topology()
> > >   File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 4749, in 
> > > _get_host_numa_topology
> > >     online_cpus = self._host.get_online_cpus()
> > >   File "/opt/stack/nova/nova/virt/libvirt/host.py", line 599, in 
> > > get_online_cpus
> > >     (cpus, cpu_map, online) = self.get_connection().getCPUMap()
> > > 
> > > I'll look into why nova is going through NUMA code paths then.
> > 
> > Oh damn, yes, I understand why now. Please file a bug against Nova for
> > this, as we must fix it as a high pripority. It was certainly not my
> > intention to break Xen when I approved this change
> 
> Here is the bug report: https://bugs.launchpad.net/nova/+bug/1425115

If you are able to test a fix easily then try the patch here:

  https://review.openstack.org/#/c/159106/

If you're able to add a comment to the review indicating that you've
confirmed it fixes Xen, that'd be useful, since there's no automated
testing of Xen that reports on reviews.

Regards,
Daniel
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