On Thu, Feb 05, 2015 at 11:21:05AM -0600, Chris Friesen wrote:
> On 02/05/2015 10:32 AM, Daniel P. Berrange wrote:
> >On Thu, Feb 05, 2015 at 10:28:56AM -0600, Chris Friesen wrote:
>
> >>For what it's worth, I was able to make hugepages work with an older qemu by
> >>commenting out two lines in
> >>virt.libvirt.config.LibvirtConfigGuestMemoryBacking.format_dom()
> >>
> >> def format_dom(self):
> >> root = super(LibvirtConfigGuestMemoryBacking, self).format_dom()
> >>
> >> if self.hugepages:
> >> hugepages = etree.Element("hugepages")
> >> #for item in self.hugepages:
> >> # hugepages.append(item.format_dom())
> >> root.append(hugepages)
> >>
> >>
> >>This results in XML that looks like:
> >>
> >> <memoryBacking>
> >> <hugepages/>
> >> </memoryBacking>
> >>
> >>
> >>And a qemu commandline that looks like
> >>
> >>-mem-prealloc -mem-path /mnt/huge-2048kB/libvirt/qemu
> >
> >With that there is no guarantee that the huge pages are being allocated
> >from the NUMA node on which the guest is actually placed by Nova, hence
> >we did not intend to support that.
>
> It's possible that the end-user didn't indicate a preference for NUMA. If
> they just asked for hugepages and we have the ability to give it to them I
> think we should do so.
>
> In the likely common case of an instance with a single NUMA node, I think
> this will likely give the desired behaviour since the default kernel
> behaviour is to prefer allocating from the numa node that requested the
> memory. As long as qemu affinity is set before it allocates memory we
> should be okay.
>
> The only case that isn't covered is if the flavor specifies multiple numa
> nodes. In that case maybe the scheduler filters should be aware of that and
> refuse to assign an instance with multiple numa nodes to a compute node with
> an older qemu.
Having the scheduler need to care about versions of software installed on
nodes is a whole heap of extra complexity for no credible gain. It is
perfectly reasonable to just mandate the newer QEMU for this IMHO and
avoid that complexity in Nova.
Regards,
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
_______________________________________________
Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
Post to : openstack@lists.openstack.org
Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
