 - Add a metric to describe how busy a processor has been over the last    two ticks by counting the number of switches and the load when    sched_clock() is called.  - If the busy metric exceeds a threshold allow the idle thread to spin    waiting for new work for a brief period to avoid using IPIs.  This    reduces the cost on the sender and receiver as well as reducing wakeup    latency considerably when it works.
 - Add a metric to describe how busy a processor has been over the last
   two ticks by counting the number of switches and the load when
   sched_clock() is called.
 - If the busy metric exceeds a threshold allow the idle thread to spin
   waiting for new work for a brief period to avoid using IPIs.  This
   reduces the cost on the sender and receiver as well as reducing wakeup
   latency considerably when it works.

Sponsored by:	Nokia

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