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

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2014-12-12 15:50, Paolo Bonzini:
> On 12/12/2014 14:00, Carew, Alan wrote:
> > The problem is deterministic control of host CPU frequency and the DPDK usage
> > model.
> > A hands-off power governor will scale based on workload, whether this is a host
> > application or VM, so no problems or bug there.
> > 
> > Where this solution fits is where an application wants to control its own
> > power policy, for example l3fwd_power uses librte_power library to change
> > frequency via apci_cpufreq based on application heuristics rather than
> > relying on an inbuilt policy for example ondemand or performance.
> > 
> > This ability has existed in DPDK for host usage for some time and VM power
> > management allows this use case to be extended to cater for virtual machines
> > by re-using the librte_power interface to encapsulate the VM->Host
> > comms and provide an example means of managing such communications.
> > 
> >  I hope this clears it up a bit.
> 
> Ok, this looks specific enough that an out-of-band solution within DPDK
> sounds like the best approach.  It seems unnecessary to involve the
> hypervisor (neither KVM nor QEMU).

Paolo, I don't understand why you don't imagine controlling frequency scaling
of a pinned vCPU transparently?
In my understanding, we currently cannot control frequency scaling without
knowing wether we are in a VM or not.

-- 
Thomas