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    SubjectRe: Increased ipw2200 power usage with dynticks
    On 2007.05.20 20:55:35 +0200, Andi Kleen wrote:
    > Björn Steinbrink <> writes:
    > >
    > > Ok, it seems that ipw2200 is just a trigger for the problem here. AFAICT
    > > the cause of the worse C state usage is that after ipw2200 has woken the
    > > cpu, acpi_processor_idle() chooses C2 (due to dma? bm? I have no
    > > idea...) as the prefered sleep state. Now without NO_HZ or when I hold
    > > down a key, there are interrupts that wake up the CPU and when
    > > acpi_processor_idle() is called again the promotion to C3/C4 happens.
    > > But with NO_HZ, there are no such interrupts, most wakeups are caused by
    > > ipw2200 and so the processor doesn't go any deeper than C2 most of the
    > > time and thus wastes lots of power.
    > The cpuidle governour code Venki is working on is supposed to address this.
    > There have been also earlier prototype patches by Adam Belay and
    > Thomas Renninger.

    Venki (at least I think it was him) also told me about cpuidle and the
    menu governor on #powertop. Unfortunately, cpuidle seems to be gone from
    acpi-test (or I'm simply still too stupid for git/gitweb). I manually
    added the cpuidle and menu governor patches on top of my 2.6.22-rc1-hrt8
    kernel, but that broke C-state duration accounting.

    On the bright side of things is power usage though, which is down to an
    incredible 13.9W in idle+ipw2200 :)


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