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    SubjectRe: [RFC] maximum latency tracking infrastructure
    Arjan van de Ven wrote:
    > Jesse Barnes wrote:
    >
    >> On Thursday, August 24, 2006 10:41 am, Arjan van de Ven wrote:
    >>
    >>> The reason for adding this infrastructure is that power management in
    >>> the idle loop needs to make a tradeoff between latency and power
    >>> savings (deeper power save modes have a longer latency to running code
    >>> again).
    >>
    >>
    >> What if a processor was already in a sleep state when a call to
    >> set_acceptable_latency() latency occurs?
    >
    >
    > there's nothing sane that can be done in that case; any wake up already
    > will cause the unwanted latency!
    > A premature wakeup is only making it happen *now*, but now is as
    > inconvenient a time as any...
    > (in fact it may be a worst case time scenario, say, an audio interrupt...)

    Surely you would call set_acceptable_latency() *before* running such
    operation that requires the given latency? And that set_acceptable_latency
    would block the caller until all CPUs are set to wake within this latency.

    That would be the API semantics I would expect, anyway.

    --
    SUSE Labs, Novell Inc.
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