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

["Carew, Alan" <alan.carew@intel.com>]

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.