How much power does KDE need?

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Honestly, I just love hacking while traveling by train - no IRC, no ICQ, no email that steals attention. However, most of the time I don't sit near a power supply socket so my laptop runs from battery. How much do you need for running KDE? I don't mean CPU or RAM ressources, but battery power. I know that you can enhance the battery lifetime by installing more RAM into your laptop - so that the hard disk has less work to do. But how much could you save by not running KDE ?

And I had time to figure out. I've fixed busy-looping in KDE-applications already in the past, but it seems there are new offenders added to our tree on a daily basis. Even if those busy-looping applications (with short timeouts) never appear as significant in the top output - they eat processing time.. and power. For my laptop, running KDE (not doing any user interaction) requires about 1.2 W/h. Thats 10%. With other words, I could hack about 10% longer if those are fixed. Thats a lot, so I started stracing to find the worst offenders. And the hitlist is:

  • artsd. No further comment necessary, its the first thing I kill (or don't even install) anyway.

  • kded (with dnotify it seems to busy-loop due to debug-output<->directory changed trigger loop)
  • klaptopdaemon. The code just does horrible stuff, including installing event listeners everywhere for no reason. Second thing to kill if you actually use a laptop.
  • kicker. One reason is the clock, which busy-loops even if nothing is to be expected to be done. But its doing a lot more, I haven't quite figured out yet what it does, but its definitely unnecessary as long as there is no user interaction.

Over the next few weeks I might try fixing those worst offenders. Any help with that is highly appreciated.