[openstack-dev] [Nova] Blueprint: standard specification of guest CPU topology

Daniel P. Berrange berrange at redhat.com
Mon Dec 2 15:43:58 UTC 2013


On Tue, Nov 19, 2013 at 12:15:51PM +0000, Daniel P. Berrange wrote:
> For attention of maintainers of Nova virt drivers

Anyone from Hyper-V or VMWare drivers wish to comment on this
proposal....


> A while back there was a bug requesting the ability to set the CPU
> topology (sockets/cores/threads) for guests explicitly
> 
>    https://bugs.launchpad.net/nova/+bug/1199019
> 
> I countered that setting explicit topology doesn't play well with
> booting images with a variety of flavours with differing vCPU counts.
> 
> This led to the following change which used an image property to
> express maximum constraints on CPU topology (max-sockets/max-cores/
> max-threads) which the libvirt driver will use to figure out the
> actual topology (sockets/cores/threads)
> 
>   https://review.openstack.org/#/c/56510/
> 
> I believe this is a prime example of something we must co-ordinate
> across virt drivers to maximise happiness of our users.
> 
> There's a blueprint but I find the description rather hard to
> follow
> 
>   https://blueprints.launchpad.net/nova/+spec/support-libvirt-vcpu-topology
> 
> So I've created a standalone wiki page which I hope describes the
> idea more clearly
> 
>   https://wiki.openstack.org/wiki/VirtDriverGuestCPUTopology
> 
> Launchpad doesn't let me link the URL to the blueprint since I'm not
> the blurprint creator :-(
> 
> Anyway this mail is to solicit input on the proposed standard way to
> express this which is hypervisor portable and the addition of some
> shared code for doing the calculations which virt driver impls can
> just all into rather than re-inventing
> 
> I'm looking for buy-in to the idea from the maintainers of each
> virt driver that this conceptual approach works for them, before
> we go merging anything with the specific impl for libvirt.


Daniel
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