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    SubjectRe: high power consumption in recent kernels
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    On Thu, 2010-07-08 at 15:23 +0200, Peter Zijlstra wrote:
    > On Thu, 2010-07-08 at 21:46 +0900, Norbert Preining wrote:
    > > Looks promising, reverting the old patch, adding that one, building,
    > > running, unplugging ppower, powertop runs now since some time,
    > > it seems that we are back to better situation:
    >
    > Hrmm, Mike seems you wrecked power usage..
    >
    > So nohz_ratelimit() prevents us from entering NOHZ when the last attempt
    > was less than 1/2 a jiffy ago (fwiw: NSEC_PER_SEC/HZ == TICK_NSEC).
    >
    > Its either entering idle or irq_exit trying to enter nohz state, if we
    > keep skipping it it means that we get enough interrupt activity to
    > render nohz useless anyway.. so not quite sure how this wrecks things..

    OK, so Arjan said the gain could come from tricking the idle governor
    into not using deeper C states. He also said he significantly cured said
    governor in .35.

    Mike could you re-run your netperf tests that showed the 10% throughput
    gain? Hopefully the fixed governor will yield the same result and we can
    kill off this ratelimit thing.


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