When you run powertop the first time (or second time), you might see
the following message:

> Loaded 100 prior measurements
> Cannot load from file /var/cache/powertop/saved_parameters.powertop
> File will be loaded after taking minimum number of measurement(s) with battery only

This is not a bug. As the messages shown, you have to run powertop and
wait it to collect enough data in order to create the
saved_parameters.powertop file. Depending on the system, the maximum
requirement is 2250 measurements. The process may take one or two
hours.

Do not rename `/var/cache/powertop/saved_results.powertop to
saved_parameters.powertop.

While this silences the program, it is not correct. The parameters are
models to improve the prediction of power consumption. Try running the
program longer while doing your normal workload.

See also: the -c, --calibrate option in manpage powertop(8)

 -- Kan-Ru Chen (陳侃如) <koster@debian.org>, Fri,  3 Jan 2020 23:28:52 +0900
