Re: [PATCH v4 00/10] VM Power Management

[Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>]

Hi Alan,

Did you make any progress in Qemu/KVM community?
We need to be sync'ed up with them to be sure we share the same goal.
I want also to avoid using a solution which doesn't fit with their plan.
Remember that we already had this problem with ivshmem which was planned
to be dropped.

Thanks
-- 
Thomas


2014-10-16 15:21, Carew, Alan:
> Hi Thomas,
> 
> > > However with a DPDK solution it would be possible to re-use the message bus
> > > to pass information like device stats, application state, D-state requests
> > > etc. to the host and allow for management layer(e.g. OpenStack) to make
> > > informed decisions.
> > 
> > I think that management informations should be transmitted in a management
> > channel. Such solution should exist in OpenStack.
> 
> Perhaps it does, but this solution is not exclusive to OpenStack and just a potential use case.
> 
> > 
> > > Also, the scope of adding power management to qemu/KVM would be huge;
> > > while the easier path is not always the best and the problem of power
> > > management in VMs is both a DPDK problem (given that librte_power only
> > > worked on the host) and a general virtualization problem that would be
> > > better solved by those with direct knowledge of Qemu/KVM architecture
> > > and influence on the direction of the Qemu project.
> > 
> > Being a huge effort is not an argument.
> 
> I agree completely and was implied by what followed the conjunction.
> 
> > Please check with Qemu community, they'll welcome it.
> > 
> > > As it stands, the host backend is simply an example application that can
> > > be replaced by a VMM or Orchestration layer, by using Virtio-Serial it has
> > > obvious leanings to Qemu, but even this could be easily swapped out for
> > > XenBus, IVSHMEM, IP etc.
> > >
> > > If power management is to be eventually supported by Hypervisors directly
> > > then we could also enable to option to switch to that environment, currently
> > > the librte_power implementations (VM or Host) can be selected dynamically
> > > (environment auto-detection) or explicitly via rte_power_set_env(), adding
> > > an arbitrary number of environments is relatively easy.
> > 
> > Yes, you are adding a new layer to workaround hypervisor lacks. And this layer
> > will handle native support when it will exist. But if you implement native
> > support now, we don't need this extra layer.
> 
> Indeed, but we have a solution implemented now and yes it is a workaround, that is until Hypervisors support such functionality. It is possible that whatever solutions for power management present themselves in the future may require workarounds also, us-vhost is an example of such a workaround introduced to DPDK.
> 
> > 
> > > I hope this helps to clarify the approach.
> > 
> > Thanks for your explanation.
> 
> Thanks for the feedback.
> 
> > 
> > --
> > Thomas
> 
> Alan.