Powertop

Does Powertop achieve better power saving than TLP?

Basically no. TLP’s default configuration is based on the same policy as Powertop’s recommendations. Refer to the following sections for details and exceptions.

Does Powertop conflict with TLP?

Powertop in interactive mode has no impact on TLP’s function.

Explanation

Powertop isn’t a power management but merely an analysis tool. You can use Powertop to view estimates about your power usage before and after installation of TLP, but TLP determines the best defaults for your system regardless of whether or not Powertop is installed.

Note

On the other hand, attempting to run powertop --auto-tune on each boot may overwrite TLP’s settings depending on the actual boot order.

Why does Powertop suggest more power saving settings with TLP already running?

Important

TLP applies maximum power savings on battery power only, so unplug AC power before checking with Powertop.

Powertop’s recommendations are quite schematic, they do not take into account frequently occurring problems with certain types of devices. For that reason TLP’s settings deviate from Powertop’s recommendations for a few but important exceptions:

Message ‘VM writeback timeout’

Powertop insists on a value of 1500 centisecs, whereas TLP’s defaults are 1500 on AC and 6000 on battery power. If you incline towards Powertop’s opinion then change the setting to:

MAX_LOST_WORK_SECS_ON_BAT=15

Message ‘SATA ALPM link power’

Some laptops refuse ALPM for particular SATA links, so it is impossible to change from max_performance to min_power. One cause may be an open link to the docking station’s drive bay when not docked.

Workaround for older X-Series ThinkPads: enter BIOS setup. Go to Security → IO Port Access and change Ultrabay access to disabled. Saves approx. 0.4 W.

Message ‘Wifi powersave’

For some Wi-Fi cards – for instance the Intel 3945abg – the Linux kernel does not support Wi-Fi power saving.

Message ‘USB autosuspend’

TLP’s default configuration intentionally exempts input devices like mice and keyboards as well as scanners handled by libsane. To enforce autosuspend nevertheless, add the device to USB_WHITELIST.

Powertop shows a very high power consumption for a device

It is impossible to measure the power consumption of individual laptop components. Therefore the readings in the ‘Device stats’ column ‘Power est.’ are rough estimations and do not provide a reliable statement.