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Thread: Is Linux Power Management Getting Better Or Worse?

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  1. #1
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    Default Is Linux Power Management Getting Better Or Worse?

    Phoronix: Is Linux Power Management Getting Better Or Worse?

    With three laptops representing different generations of mobile hardware, we loaded up the past four stable releases of Fedora Linux plus the most recent Fedora 14 Alpha release and then carried out an arsenal of tests looking at how the battery power consumption rate has changed since 2008. If you are concerned at all about running Linux on your battery-powered mobile devices, this article is worth reading.

    http://www.phoronix.com/vr.php?view=15301

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    It's not just about software improving but also hardware. 2.6.35 introduced the intel_idle driver, which makes a massive difference for CPUs that support it but none of those tested do.

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    I would say that the higher power consumption on the Core2 notebooks are due to the open source graphics drivers not being very well optimized in this regard.
    It's too bad there aren't any netbook performance numbers. My guess is that we would see something like what the tests showed with the R52.
    I remember installing Fedora 10 on my Eee PC 1000H with a usb flash drive, although it had to be formated in a very particular way in order to boot.

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    Quote Originally Posted by Chewi View Post
    It's not just about software improving but also hardware. 2.6.35 introduced the intel_idle driver, which makes a massive difference for CPUs that support it but none of those tested do.
    I use the 2.6.35 (maverick), on an Acer One netbook. Don't know if it really uses the intel_idle instead of acpi_idle, but its idle power usage is abysmal. Powertop reports lots of load balancing ticks (which is another bug that is supposed to be fixed in 2.6.35) and generally the laptop is burning hot.

    I wish the linux kernel developers where a bit more concerned on power usage. It's killing the netbook experience (makes Microsoft's solutions much better, which shouldn't be the case)

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    mind you, it may well be the distro vendors' fault (Canonical in my case), that have not set up things properly, to take advantage of power saving features. Or as others here have mentioned, the CPU might not be the culprit, rather the GPU or some other subsystem.

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    Quote Originally Posted by ioannis View Post
    I use the 2.6.35 (maverick), on an Acer One netbook. Don't know if it really uses the intel_idle instead of acpi_idle, but its idle power usage is abysmal. Powertop reports lots of load balancing ticks (which is another bug that is supposed to be fixed in 2.6.35) and generally the laptop is burning hot.

    I wish the linux kernel developers where a bit more concerned on power usage. It's killing the netbook experience (makes Microsoft's solutions much better, which shouldn't be the case)
    intel_idle is chosen over acpi_idle if your CPU supports it. I gather the Atom does. /sys/devices/system/cpu/cpuidle/current_driver should report the name of the driver being used. I also use i7z to monitor its behaviour but I don't know whether this works on the Atom. Maybe give it a try.

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    Quote Originally Posted by Chewi View Post
    intel_idle is chosen over acpi_idle if your CPU supports it. I gather the Atom does. /sys/devices/system/cpu/cpuidle/current_driver should report the name of the driver being used. I also use i7z to monitor its behaviour but I don't know whether this works on the Atom. Maybe give it a try.
    thanks for tip, it does use the intel_idle. And no, i7z does not work on the Atom. It's for Nehalem based architectures.

  8. #8
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    It would be hard to argue that power management is getting worse. When I got my i7 there wasn't even proper P-state support for frequency scaling. A proper test would throw on some minimal distro like Gentoo or Arch, add the linux-phc patchset for dynamic undervolting, enable kernel frequency scaling, do some powertop tweaks, use opensource drivers with supported power management.

    Surely power management isn't getting worse. Probably more like a side-effect of whatever happens to be running in a default Fedora install.

  9. #9

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    Have you tested to make sure that polling acpi every second doesn't have a noticeable effect on (idle) power use? If wakeups have been brought under control in recent releases, could the additional wakeups caused by too-frequent polling by the test suite wipe out some of the gains made?

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    I have a couple things to comment on with this;
    1) pushing the hardware to its limits will disable power management. As a result ONLY the FIRST test was particularly valid. The rest could be only related to how much harder the hardware is actually being pushed by code that is more optimized for it, i.e. making use of hardware that was idle before will improve performance at the expense of power consumption.
    2) Fedora 14 is running DEBUGGING KERNELS STILL. Come on -- you've been caught making this mistake MANY MANY MANY times before!

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