sched/deadline: Don't balance during wakeup if wakee is pinned

Use nr_cpus_allowed to bail from select_task_rq() when only one cpu
can be used, and saves some cycles for pinned tasks.
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1413253360-5318-2-git-send-email-wanpeng.li@linux.intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/deadline.c

@@ -933,6 +933,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
 	struct task_struct *curr;
 	struct rq *rq;
 
+	if (p->nr_cpus_allowed == 1)
+		goto out;
+
 	if (sd_flag != SD_BALANCE_WAKE)
 		goto out;