Ubuntu 24.04 Improves Power Efficiency on Laptops

A new version of Power Profiles Daemon in Ubuntu 24.04 offers power efficiency improvements for laptop users, but those with modern AMD devices may see the biggest gains.

Release notes for the power-profiles-daemon package uploaded to Ubuntu 24.04 this week state that it is now “battery-state aware” and that “some drivers use a more power efficient state when using the balanced profile on battery”.

While the power profiles daemon is low-level it enables the Power Mode options shown in the Quick Settings menu: “balanced” (default), “power saver”, and on systems where it’s supported by drivers “performance” — this update tweaks the “balanced” option.

On Intel and AMD hardware able to use P-State drivers (which, IIRC, is Skylake and Zen 2 upwards, respectively) the “balanced” profile is now mapped to a new balance_power Energy Performance Preference (EPP) profile rather than balance_performance.

When a power cable is connected to the laptop the “balanced” mode swaps to the balance_performance profile in the background. This technically means Ubuntu now has 4 power modes although only 3 are exposed in the GUI.

For Intel, this update also increases the energy_perf_bias to 8, up from 6.

Since higher numbers are more power efficient this may — I make no promises, heh — mean Intel users see better power savings in Ubuntu 24.04 than earlier versions (to a varying degree; depends on what else is running, the device config, other settings, etc).

P-state drivers provide more nuanced, flexible, and granular power and processor frequency scaling controls than acpi-cpufreq, though the latter remains widely used in Linux distros as it works well and supports a much wider range of hardware.

Want to know which power driver Ubuntu is using on your device? Open a Terminal window and run the following command (it doesn’t change anything, don’t worry):

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_driver

If able, the command prints the power governor/scaling driver in use (for each core), e.g, intel_pstate, amd_pstate, oracpi-cpufreq.

Other changes in power-profiles-daemon 0.21 include a crop of code optimisations, a flurry of fixes for the powerprofilesctl command-line tool, improved documentation, and autocompletion for both bash and ZSH (if install path provided for the latter).

Finally, the systemd service lockdown settings are said to now be “restricted even more”, which is reassuring (assuming you, unlike I, know what that means).

In all, a nice set of improvements and yet more reason to upgrade to Ubuntu 24.04 when it’s released (hopefully) on April 25, 2024.

Thanks Mario