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    SubjectRe: [RFC PATCH 02/15] nohz_task: Avoid nohz task cpu as non-idle timer target
    On Mon, Dec 20, 2010 at 04:47:58PM +0100, Peter Zijlstra wrote:
    > On Mon, 2010-12-20 at 16:24 +0100, Frederic Weisbecker wrote:
    > > Unbound timers are preferably targeted for non idle cpu. If
    > > possible though, prioritize idle cpus over nohz task cpus,
    > > because the main point of nohz task is to avoid unnecessary
    > > timer interrupts.
    >
    > Oh is it?
    >
    > I'd very much expect the cpu that arms the timer to get the interrupt. I
    > mean, if the task doesn't want to get interrupted by timers,
    > _DON'T_USE_TIMERS_ to begin with.
    >
    > So no, don't much like this at all.

    I suspect TIMER_NOT_PINNED has been introduced to save some power by
    avoiding to wake up idle cpus.

    This is used by mod_timer(), schedule_timeout(), mod_timer_pending()
    So that's widely used and removing that could have a deep impact on
    power.


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