Linux 5.9 To Allow For Toggling Energy Efficiency Mode On Kaby Lake CPUs

The patches talked about last month for a new "energy efficiency" tunable for the Intel P-State driver for Kabylake / Coffeelake CPUs is set to go into Linux 5.9 for those wanting to increase the energy efficiency of these CPUs on Linux albeit with reduced performance.

The existing behavior with Intel Kabylake / Coffeelake CPUs on Linux has been for the P-State driver to set the relevant MSR for ensuring maximum performance with opening up all of the high performance states. But now slated for introduction with Linux 5.9 is the "energy_efficiency_enable" node via sysfs that can allow setting the CPU in its more energy efficient mode. This is for those wanting lower energy use and heat output albeit with slower performance on these select Intel CPUs.

In addition to the energy efficiency enable knob, there is also the "energy_performance_preference" patch that is also queued up for offering more control over the EPP (Energy Performance Preference) operating mode.

The work by Intel seems to be driven at least in part by Google for Chromebook usage. As of yesterday the patches have been queued into the Linux power management "linux-next" Git branch ahead of the Linux 5.9 cycle.

That pull yesterday also adds Intel Sapphire Rapids support to the RAPL (Runtime Average Power Limiting) Intel driver.