sched/numa: Rename nr_running and break out the magic number

This is simply a preparation patch to make the following patches easier
to read. No functional change.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20201120090630.3286-2-mgorman@techsingularity.net

kernel/sched/fair.c

@@ -1559,7 +1559,7 @@ struct task_numa_env {
 static unsigned long cpu_load(struct rq *rq);
 static unsigned long cpu_runnable(struct rq *rq);
 static unsigned long cpu_util(int cpu);
-static inline long adjust_numa_imbalance(int imbalance, int nr_running);
+static inline long adjust_numa_imbalance(int imbalance, int dst_running);
 
 static inline enum
 numa_type numa_classify(unsigned int imbalance_pct,
@@ -8991,16 +8991,18 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
 	}
 }
 
-static inline long adjust_numa_imbalance(int imbalance, int nr_running)
+#define NUMA_IMBALANCE_MIN 2
+
+static inline long adjust_numa_imbalance(int imbalance, int dst_running)
 {
 	unsigned int imbalance_min;
 
 	/*
 	 * Allow a small imbalance based on a simple pair of communicating
 	 * tasks that remain local when the source domain is almost idle.
 	 */
-	imbalance_min = 2;
-	if (nr_running <= imbalance_min)
+	imbalance_min = NUMA_IMBALANCE_MIN;
+	if (dst_running <= imbalance_min)
 		return 0;
 
 	return imbalance;