KDE and Linux are power hogs

Acer claims my TravelMate TimeLine 8371 notebook should deliver over eight hours of battery life. However, that was measured with Windows Vista Business as it’s operating system. I’m using Linux, and because Windows and Linux are different the power consumption should be different as well. The long battery life of 8371 was an important selling point for me, so I decided to measure how much power is consumed by various Linux distributions with PowerTOP.

The distributions I tested were Ubuntu 9.10, Kubuntu 9.10 and the Fedora 12 with KDE. I also wanted to test OpenSUSE 11.2 and Chakra Alpha 4, but while they didn’t work on my 8371. When I tried to boot from the USB flash drives containing the Live systems of those two distributions by using the boot menu you get when press F12 on the 8371, the boot menu froze. My desktop had no problem booting from the USB flash drives with OpenSUSE and Chakra, so I assume my USB flash drives are fine and that it’s Acer’s fault because there is a bug in the BIOS of the 8371. If I’m correct this freezing occured with BIOS 1.18. I haven’t tried this with the latest version, BIOS 1.27, yet. On the other hand, considering that my 8371 had no problems with the Ubuntu, Kubuntu and Fedora Live USB’s, OpenSUSE and Chakra must be doing certain things differently which causes my BIOS to choke on the Live USB’s with those two distributions. I’ve posted topics concerning these problems on the forums of the two distributions here and here. On Chakra’s forum a solution was suggested, I haven’t tried if that works yet. An alternative is to install them with PXE so the network interface (ethernet port) can be used, but I’d rather not do that because it requires more effort. Besides giving the suggested solution a try, I’ll make sure to upgrade to the latest BIOS again. I’ll send Acer an e-mail to ask if they have a changelog of their BIOS versions as well.

Of course I used a common testing methodology for a good comparison. I installed all three distributions to my Intel X-25M solid state drive. I didn’t mess with power management settings, so all settings were at their defaults. As far as I know power management settings are the same for all three, because all dim the display when the computer is idle and reduce the backlight brightness when the notebook is on battery power. I always turned Bluetooth off with the keyboard key combination, because it’s on by default. I have to figure out a way to disable it by default so I don’t have to disable it everytime I start up my notebook, because I never use Bluetooth. I tested with WiFi on and off to see what impact it would have in power consumption. PowerTOP is available in the standard repositories of all three distributions. I made sure to start PowerTOP as root (sudo on Ubuntu and Kubuntu) because it should show more information then. I waited a few minutes to see if the reported power consumption remained steady and then noted it. Besides the X25-M which was used to replace the hard disk drive, my 8371 was completely standard and nothing was connected via USB ports. Measurements were made after starting up the Linux distributions and opening Konsole or the GNOME Terminal immediately, no other applications were started. I didn’t follow any of PowerTOP’s suggestions to save more power, I was interested in how much power the distributions would consume out of the box, without any tweaking. Desktop effects were enabled on all distributions if I remember correctly. One last thing to be mentioned is that all measurements were made while the 8371 was running on battery power, if it’s not PowerTOP won’t even work as far as I know.

Power consumption in W by distribution
Distribution WiFi on WiFi off
Ubuntu 9.10 9,7 8,5
Kubuntu 9.10 11,6 10,3
Fedora 12 KDE 11,1 9,6

Now contrast this with the figure of 5,9 Watt for Microsoft Windows Vista Business 32-bit mentioned here. Adding insult to injury, the 8371 version tested there used a dual-core Intel Core 2 Duo SU9400 CPU and 4 GB RAM while my 8731 uses a single-core SU3500 and 3 GB RAM. The difference between these CPU’s is notable, because the SU9400 is rated for a thermal design power of 10 Watt while the SU3500 is rated for 5,5 Watt. That’s a difference of 2,6 Watt considering the lowest power consumption I measured with WiFi disabled on Ubuntu 9.10. A difference of almost 30%. And then we haven’t even taken into account the lower power consumption of my CPU and solid state drive!

On the Ubuntu Forums a person who possesses an Acer Aspire TimeLine 3810T (the consumer version of my TravelMate TimeLine 8371, using the same SU3500 CPU) also investigated the power consumption. According to him Ubuntu 9.10 uses 2,4 Watt extra compared to Windows Vista. Another person who replied speculates that the cause might lie in the Linux software because it’s power management is simply not as efficient as in Windows Vista.

Besides that, according to my investigation, there is a very significant difference in power consumption when KDE and GNOME are compared. The only difference between Kubuntu 9.10 and Ubuntu 9.10 is that Kubuntu uses KDE and Ubuntu uses GNOME, so KDE must cause the extra power consumption of 2 Watt. I need to figure out if anything can be done to fix this relatively high power consumption caused by Linux and KDE and what causes it. I will write another post when I know more. Meanwhile I’m disappointed that Linux is inferior when compared to Windows Vista (and by extension probably Windows 7) when it comes to power management.

4 thoughts on “KDE and Linux are power hogs”

  1. Pingback: Problems with power saving on Kubuntu « Information Overload

  2. Hi from Germany,

    I tried to install Chakra Linux Alpha 5 on my Travelmate 8371 with the SU3500 CPU but it didn’t work. Did you get Chakra installed on your machine yet or was that your last attempt?

    I like KDE a lot but with all the deamons in the background (Akonadi/Nepomuk etc.) it is not only a power hog but also one of CPU usage. It slowed down my machine while surfing, listening music with amarok und managing multiple calenders. Therefore I would like to try Chakra Linux.

    Nice blog anayway 🙂

  3. Hi Thomas,

    Thanks for your comment. I’m not sure what your problem is exactly, but I did manage to get the Live CD started. Didn’t attempt to install though. But now that Alpha 5 is released I probably will attempt to install it soon.

    Please take a look at this topic for the solution. That is, if you also were affected by the problem that the Chakra Live USB would freeze the 8371.

  4. Pingback: Hiatus « This week in panospace

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