Comment 0 for bug 1885730

In a recent merge from Debian we lost ondemand.service, meaning all CPUs now run in Turbo all the time when idle, which is clearly suboptimal.

The discussion in bug 1806012 seems misleading, focusing on p-state vs other drivers, when in fact, the script actually set the default governor for the pstate driver on platforms that use pstate. Everything below only looks at systems that use pstate.

pstate has two governors: performance and powerstate. performance runs CPU at maximum frequency constantly, and powersave can be configured using various energy profiles energy profiles:

- performance
- balanced performance
- balanced power
- power

It defaults to balanced performance, I think, but I'm not sure.

Whether performance governor is faster than powersave governor is not even clear. https://www.phoronix.com/scan.php?page=article&item=linux50-pstate-cpufreq&num=5 benchmarked them, but did not benchmark the individual energy profiles.

For a desktop/laptop, the expected behavior is the powersave governor with balanced_performance on AC and balanced_power on battery.

I don't know about servers or VMs, but the benchmark series seems to indicate it does not really matter much performance wise.

I think most other distributions configure their kernels to use the powersave governor by default, whereas we configure it to use the performance governor and then switch it later in the boot to get the maximum performance during bootup. It's not clear to me that's actually useful.