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    SubjectRe: [linux-pm] idle-test patches queued for upstream
    Date
    On Thursday 27 May 2010 04:42:23 Len Brown wrote:
    > Please look over and test this patch set.
    > (If you test linux-next, you already have it)
    >
    > There are a few simple patches, leading up to a new intel_idle driver.
    >
    > Note that you can get the patch series as a single patch here:
    > http://ftp.kernel.org/pub/linux/kernel/people/lenb/idle/patches/2.6.34/idle-test-2.6.34.diff.gz
    >
    > or pull from this git branch
    > git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6.git idle-test
    >
    > Both are vs 2.6.34.
    >
    > Why is it good to have a native intel_idle driver?
    >
    > Basically, we think we can do better than ACPI.
    Why exactly? Is there any info missing in the ACPI tables?
    Or is this just to be more independent from OEMs?

    > Indeed, on my (production level commerically available) Nehalem desktop
    > the ACPI tables are broken and an ACPI OS idles at 100W. With this
    > driver the box idles at 85W.
    What exactly was broken there?

    IMO this is a step backward.
    CPUfreq runs rather well on nearly every machine supporting it without
    tons of static frequency tables in kernel. Even powernow-k8 might get merged
    into acpi-cpufreq.

    Intel set up a huge ACPI API for this and now it's not used anymore?!?
    Will these parts get obsoleted in a future spec?
    While for C-states there are not that many static entries needed, another
    drawback could be that OEMs will disable/hide C-states on purpose.

    Using ACPI table based C-states by default and using intel_idle.enable=1
    or similar for workarounds sounds safer.
    At least as long as the driver is experimental.

    Does Windows use ACPI C-state info for idle?

    Thanks,

    Thomas


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