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    SubjectRe: [PATCH 0/3] cpu: idle state framework for offline CPUs.
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    On Wed, 2009-08-12 at 13:58 +0200, Pavel Machek wrote:
    > Hi!
    >
    > > May be having (to pick a number) 3 possible offline states for all
    > > platforms with one for halt equivalent and one for deepest possible that
    > > CPU can handle and one for deepest possible that platform likes for
    > > C-states may make sense. Will keeps things simpler in terms of usage
    > > expectations and possibly reduce the misuse oppurtubity?
    >
    > Maybe just going to the deepest offline state automatically is the
    > easiest option?
    >
    > cpu hotplug/unplug should be rare-enough operation that the latencies
    > do not really matter, right?

    Ha, it uses kstopmachine, anybody caring about hotplug latencies is
    insane.

    And yeah, I'm not quite sure what this user-interface is good for
    either. Having an in-kernel management layer where you can register
    various idle routines makes sense. But exposing it to userspace,.. not
    so much.

    The idle thread can select an idle routine under constraints of the QoS
    latency constraints, the unplug loop however should indeed select the
    one that is available to dead cpus (not all idle routines are available
    from what people tell me), and yields the best power savings.





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