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Subject: sched: Disable TTWU_QUEUE on RT
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 13 Sep 2011 16:42:35 +0200
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.9-rt3.tar.xz
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(+)
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -46,11 +46,16 @@ SCHED_FEAT(LB_BIAS, false)
*/
SCHED_FEAT(NONTASK_CAPACITY, true)
+#ifdef CONFIG_PREEMPT_RT_FULL
+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.
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