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

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

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

Regards,
Daniel
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