[libvirt] Non-contiguous NUMA cell numbers

[Roy Golan]

On Mon, Jan 4, 2016 at 12:18 PM, Andrea Bolognani <abologna at redhat.com>
wrote:

> n Mon, 2016-01-04 at 07:57 +0100, Michal Privoznik wrote:
> > On 23.12.2015 17:14, Andrea Bolognani wrote:
> > > Hi all,
> > >
> > > libvirt currently doesn't allow you to configure a guest with something
> > > like
> > >
> > >   <cpu>
> > >     <topology sockets='2' cores='5' threads='8'/>
> > >     <numa>
> > >       <cell id='0' cpus='0-39' memory='1048576' unit='KiB'/>
> > >       <cell id='16' cpus='40-79' memory='1048576' unit='KiB'/>
> > >     </numa>
> >
> > This says you are configuring GUEST NUMA nodes, and last time I checked
> > qemu did not support non-continuous NUMA nodes. So, whatever your HOST
> > topology is, in GUEST you want NUMA nodes to be continuous.
>
> I checked again and, as you and Daniel suggested, QEMU does not support
> non-contiguous NUMA nodes, eg.
>
>   qemu-kvm                                   \
>     -m 2048                                  \
>     -smp 80,sockets=2,cores=5,threads=8      \
>     -numa node,nodeid=0,cpus=0-39,mem=1024   \
>     -numa node,nodeid=16,cpus=40-79,mem=1024
>
> outputs
>
>   qemu-kvm: numa: Node ID missing: 15
>
> so indeed there's a very good reason for libvirt to reject that NUMA
> configuration.
>
>

Thanks you all for all the input. oVirt will follow this configuration
limitation and enforce it then.


Cheers.
>
> --
> Andrea Bolognani
> Software Engineer - Virtualization Team
>
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