Virtual CPUFreq Driver Coming With Linux 6.13 For Better Power/Performance Within VMs

Earlier this week was the main power management updates for Linux 6.13 that included switching AMD EPYC Turin to using the amd_pstate driver on supported systems. Sent out this weekend was another set of power management updates that also includes a notable addition: the virtual CPUFreq driver.

Included now for Linux 6.13 is the virtual-cpufreq driver as a virtualized CPU frequency scaling driver. The virtual-cpufreq driver is intended for guest virtual machine (VM) kernels for helping to improve the performance and power of workloads operating within VMs.

This Virtual CPUFreq driver developed by Google engineers will send the frequency of vCPUs as a hint to the host and in turn the host can use that hint to schedule the vCPU threads and decode the physical CPU frequency. This driver also allows for updating the guest's frequency scaling factor periodically for allowing accurate per-entity load tracking within the guests.

It will be interesting to see the impact in practice on power/performance for finally having this Virtual CPUFreq driver going mainline. Back when Google engineers first presented the work last year they were talking of dramatic VM performance and power efficiency benefits.

The Virtual CPUFreq driver is the main exciting element of the secondary power management updates for the in-development Linux 6.13 kernel.