How do I make Powertop's suggestions permanent?

Question

When I run Powertop, and look at the Tunables screen, about twenty things are listed as Bad. I can toggle these to Good by pressing enter, and when I do so, projected battery lifetime doubles.

How can I make these changes persist? (I'm on Fedora 18, by the way, with Powertop 2.2)

Solution

Powertop is not a permanent tool, as you know, so you will have to setup your system to run the commands through sysctl, udev, systemd units, scripts, whatever...

In order to see what commands are used by powertop you will have to run powertop --html BEFORE MAKING ANY CHANGES, that is, BEFORE toggling the settings from Bad to Good. If you already tuned for maximum battery life, undo your changes and run powertop --html again.

This is what the output should look like:

Comments

[mattdm]

I have no /etc/rc.conf. Also, powertop doesn't seem to be suggesting any commands to run. (I think it did that in an older version.)

[schaiba]

Create it if it isn't there. Use powertop --html and open the resulting file, going to the section called 'Software Settings in need of Tuning'

[mattdm]

If I create that file, I'm quite sure it will do nothing on my system. And the html output has no section by that name. There is Optimal Tuned Software Settings, but that just lists items like "Enable SATA link power Managmenet for host0", with no commands.

[schaiba]

My bad, that was meant to be rc.local. Fedora has , IIRC, a systemd unit file that will run that.

[mattdm]

Thanks, yeah, that would work. However, the key problem still stands: powertop --html (or anything else I can see) still doesn't tell me any actual commands. I assume they're mostly kernel tunables, so they really should go in /etc/sysctl.conf or under /etc/sysctl.d/, but I'm not sure what should be set (or to what values).

[schaiba]

I'm not on Fedora, I'm on Arch, and not only I have that section, but I do have the suggested commands. Perhaps anyone using Fedora could help further.

[mattdm]

AH! The part in all caps is exactly what I was missing.

[mattdm]

Excitingly, some of the advice appears to be backwards. For example, it says iw dev wlan0 set power_save off, but turning it on is what changes the setting to "Good".

[yorkshiredev]

Adding some information as I came accross this question : Arch initscripts are handled by systemd, see the wiki for more details : wiki.archlinux.org/index.php/Initscripts‎

[Peng]

There may be particular settings e.g. USB device sleep that you might want to disable from auto-tuning. It'd be nice to have a way to do that.