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Thread: Nailing Down The Linux Kernel Power Regressions

  1. #1
    Join Date
    Jan 2007

    Default Nailing Down The Linux Kernel Power Regressions

    Phoronix: Nailing Down The Linux Kernel Power Regressions

    For those that missed it, now that I've been back in the office for a few weeks and caught up on the other benchmarks and articles for May and beginning the work for June, I'm back to looking into the Linux kernel power regressions reported more than a month ago -- i.e. Linux Has Major Power Regression and Another Major Linux Power Regression Spotted...

  2. #2
    Join Date
    Nov 2009


    well done !

  3. #3
    Join Date
    Dec 2007
    Edinburgh, Scotland


    I thought this was traced back a while ago?

    Have you tried creating a cut down bare bones kernel? This should make life much easier and quicker for bisecting over a large number of versions. Of course you'd need to check the problem still exists first in the cut down kernel

    If you need help with this Michael please give me a shout

  4. #4
    Join Date
    Dec 2009


    Good to see it's not forgotten. Please keep up the good work!

  5. #5
    Join Date
    Apr 2010


    Maybe IBM, Google, Oracle and co could be interested in supporting you? ; )
    Splendid work!

  6. #6


    are you using ccache or distcc.

  7. #7
    Join Date
    Sep 2010

    Default use a modded battery for power measurement?

    ... still needing to monitor them for manually toggling the AC power / battery. With that said, I'm still looking for a UPS power system (or a smart AC power meter) with ...
    How about modifying a worn out battery by completely removing its cells and connecting a power supply where the cells had been connected? Then do something like:

    grep "present rate:" /proc/acpi/battery/BAT0/state
    grep "present voltage:" /proc/acpi/battery/BAT0/state

    Warning: Won't eat your cat but might otherwise be harmful (or might not work at all).


    Edit: Please check that number of cells and the voltage of power supply matches
    Last edited by frief; 06-01-2011 at 05:45 PM. Reason: added caveat

  8. #8
    Join Date
    Oct 2009


    This dude claims that he can read out cheap power meters on his ubuntu server:

  9. #9
    Join Date
    Oct 2008


    Just my idea:

    Point a web-cam to this device, do a little OCR magic and you have your numbers.

    BTW Michael:

    I just stumbled across a patch for (soon to arrive) version

    Maybe this small patch solves the power regression.

    I'm currently building a vanilla 2.6.39 kernel with this patch applied. Tomorrow i will compare it with a completely vanilla kernel. Maybe the power consumption is significantly lower with this patch.

  10. #10
    Join Date
    Jun 2011

    Default Better way to mesure power


    In order to measure power consumption I'd suggest to use multimeters instead of an UPS. The precision of the UPS is not known and it can change greatly from a manufacturer to another leading to unreproducible results.

    A bit over your budget ($140 to $150) but a better solution would be to use two VA18B DMM with usb interface, one to measure voltage, the other to measure current and then combine the two to have power.

    At the VA18 is $70 and at you can get a software to read data from usb.

    It involves a little "surgery" on the power chord in order to measure the current (you must cut one cable and attach 2 banana plugs to put the amper-meter serially) but the measures will be better then with a reading from a UPS.

    If needed I can provide a more detailed schematic.

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