sched/fair: Compile out NUMA code entirely when NUMA is disabled

Scheduler code is very hot and every little optimization counts. Instead
of constantly checking sched_numa_balancing when NUMA is disabled,
compile it out.

Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Change-Id: I7334594fbe835f615a199cfe02ee526135abab06

kernel/sched/fair.c

@@ -2480,7 +2480,8 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
 	struct numa_group *ng;
 	int priv;
 
-	if (!static_branch_likely(&sched_numa_balancing))
+	if (!IS_ENABLED(CONFIG_NUMA_BALANCING) ||
+	    !static_branch_likely(&sched_numa_balancing))
 		return;
 
 	/* for example, ksmd faulting in a user's mm */
@@ -12226,7 +12227,8 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
 		entity_tick(cfs_rq, se, queued);
 	}
 
-	if (static_branch_unlikely(&sched_numa_balancing))
+	if (IS_ENABLED(CONFIG_NUMA_BALANCING) &&
+	    static_branch_unlikely(&sched_numa_balancing))
 		task_tick_numa(rq, curr);
 
 	update_misfit_status(curr, rq);