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    Subject[patch 0/2] RFC sched: Change nohz ilb logic from poll to push model
    Existing nohz idle load balance (ilb) logic uses the pull model, with one
    idle load balancer CPU nominated on any partially idle system and that
    balancer CPU not going into nohz mode. With the periodic tick, the
    balancer does the idle balancing on behalf of all the CPUs in nohz mode.

    This is not very optimal and has few issues:
    * the balancer will continue to have periodic ticks and wakeup
    frequently (HZ rate), even though it may not have any rebalancing to do on
    behalf of any of the idle CPUs.
    * On x86 and CPUs that have APIC timer stoppage on idle CPUs, this periodic
    wakeup can result in an additional interrupt on a CPU doing the timer
    * The balancer may end up spending a lot of time doing the balancing on
    behalf of nohz CPUs, especially with increasing number of sockets and
    cores in the platform.

    The alternative is to have a push model, where all idle CPUs can enter nohz
    mode and busy CPU kicks one of the idle CPUs to take care of idle balancing
    on behalf of a group of idle CPUs.

    Following patches tries that approach. There are still some rough edges
    in the patches related to use of #defines around the code. But, wanted
    to get opinion on this approach as an RFC (not for inclusion into the
    tree yet).


    Signed-off-by: Venkatesh Pallipadi <>
    Signed-off-by: Suresh Siddha <>


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      Last update: 2009-06-17 20:39    [W:0.030 / U:11.564 seconds]
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