linux.conf.au, January 2003
      PROGRAMMING: kernel/sched.c

 	/*
 	 * One of the idle_cpu_tick() and busy_cpu_tick() functions will
 	 * get called every timer tick, on every CPU. Our balancing action
 	 * frequency and balancing agressivity depends on whether the CPU is
 	 * idle or not.
 	 *
 	 * busy-rebalance every 250 msecs. idle-rebalance every 1 msec. (or on
 	 * systems with HZ=100, every 10 msecs.)
 	 */
 	#define BUSY_REBALANCE_TICK (HZ/4 ?: 1)
 	#define IDLE_REBALANCE_TICK (HZ/1000 ?: 1)
 	
 	static inline void idle_tick(runqueue_t *rq)
 	{
 		if (jiffies % IDLE_REBALANCE_TICK)
 			return;
 		spin_lock(&rq->lock);
 		load_balance(rq, 1);
 		spin_unlock(&rq->lock);
 	}
 	
 	#endif