sched/fair: Optimize find_busiest_queue()

Use for_each_cpu_and() and thereby avoid computing the capacity for
CPUs we know we're not interested in.

Reviewed-by: Paul Turner <pjt@google.com>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-lppceyv6kb3a19g8spmrn20b@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

@@ -4946,7 +4946,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 	unsigned long busiest_load = 0, busiest_power = 1;
 	int i;
 
-	for_each_cpu(i, sched_group_cpus(group)) {
+	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
 		unsigned long power = power_of(i);
 		unsigned long capacity = DIV_ROUND_CLOSEST(power,
 							   SCHED_POWER_SCALE);
@@ -4955,9 +4955,6 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 		if (!capacity)
 			capacity = fix_small_capacity(env->sd, group);
 
-		if (!cpumask_test_cpu(i, env->cpus))
-			continue;
-
 		rq = cpu_rq(i);
 		wl = weighted_cpuload(i);