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