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From 1b8c8ade10b0b08dd7f7c2068683a78571967037 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 13 Sep 2011 16:42:35 +0200
Subject: [PATCH 123/191] sched: Disable TTWU_QUEUE on RT

The queued remote wakeup mechanism can introduce rather large
latencies if the number of migrated tasks is high. Disable it for RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/sched/features.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 1bc2b158fc51..b47967d00570 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -46,11 +46,16 @@ SCHED_FEAT(DOUBLE_TICK, false)
  */
 SCHED_FEAT(NONTASK_CAPACITY, true)
 
+#ifdef CONFIG_PREEMPT_RT
+SCHED_FEAT(TTWU_QUEUE, false)
+#else
+
 /*
  * Queue remote wakeups on the target CPU and process them
  * using the scheduler IPI. Reduces rq->lock contention/bounces.
  */
 SCHED_FEAT(TTWU_QUEUE, true)
+#endif
 
 /*
  * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
-- 
2.19.1