From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 6 Jun 2011 12:12:51 +0200
Subject: sched: Limit the number of task migrations per batch
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 6f0761a223dbae2ebcccde8e2dd4a1e961883a91
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

Put an upper limit on the number of tasks which are migrated per batch
to avoid large latencies.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 kernel/sched/core.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -58,7 +58,11 @@ const_debug unsigned int sysctl_sched_fe
  * Number of tasks to iterate in a single balance run.
  * Limited because this is done with IRQs disabled.
  */
+#ifndef CONFIG_PREEMPT_RT_FULL
 const_debug unsigned int sysctl_sched_nr_migrate = 32;
+#else
+const_debug unsigned int sysctl_sched_nr_migrate = 8;
+#endif
 
 /*
  * period over which we average the RT time consumption, measured