Re: [libvirt] Non-contiguous NUMA cell numbers
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.
</cpu>
with the following error:
XML error: Exactly one 'cell' element per guest NUMA cell allowed,
non-contiguous ranges or ranges not starting from 0 are not allowed
The error message is very specific about not allowing gaps in NUMA cell
numbering; however, on the very same host, I have
$ numactl --hard | head -1
available: 4 nodes (0-1,16-17)
so gaps in numbering are definitely possible, at least on ppc64.
Should we consider relaxing this requirement and allow
arbitrarily-numbered NUMA cells? Is there a specific reason why it was
forbidden in the first place?
Cheers.
Michal