Reducing desktop power usage while idle

While remotely monitoring my desktop session with powertop while it was idle (screensaver active) I noticed that a few processes cause a lot of activity, and keeping the CPU from going into the PC7 state (the complete cpu package deepest sleep state). Most notably firefox and it’s plugin-container cause frequent wakeups.

I wrote a short script that listens on dbus for screensaver ActiveChanged messages, and either sends a STOP or a CONT signal to firefox and the plugin-container. This script makes my desktop go from 20W to 19W of power when I am not using it.

import subprocess
import datetime

import dbus, gobject
from dbus.mainloop.glib import DBusGMainLoop

stoplist = ['firefox', 'plugin-container', 'steam']
def msg2_cb(msg):
	dt = datetime.datetime.now()
	if (msg):
		for name in stoplist:
			subprocess.call(["killall", "-STOP", name])
	else:
		for name in stoplist:
			subprocess.call(["killall", "-CONT", name])

if __name__ == '__main__':
	DBusGMainLoop(set_as_default=True)
	bus = dbus.SessionBus()
	bus.add_signal_receiver(msg2_cb, 'ActiveChanged', None, None, '/org/gnome/ScreenSaver')
	mainloop = gobject.MainLoop ()
	mainloop.run ()

The obvious caveat is that any downloads by firefox are also stopped if the screensaver becomes active.