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[PATCH 2/5] sched/numa: Disable sched_numa_balancing on UMA systems

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From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

commit c3b9bc5bbfc3750570d788afffd431263ef695c6 upstream.

Commit 2a1ed24 ("sched/numa: Prefer NUMA hotness over cache hotness")
sets sched feature NUMA to true. However this can enable NUMA hinting
faults on a UMA system.

This commit ensures that NUMA hinting faults occur only on a NUMA system
by setting/resetting sched_numa_balancing.

This commit:

  - Makes sched_numa_balancing common to CONFIG_SCHED_DEBUG and
    !CONFIG_SCHED_DEBUG. Earlier it was only in !CONFIG_SCHED_DEBUG.

  - Checks for sched_numa_balancing instead of sched_feat(NUMA).

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1439290813-6683-3-git-send-email-srikar@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 kernel/sched/core.c  | 14 +++++---------
 kernel/sched/fair.c  |  4 ++--
 kernel/sched/sched.h |  6 ------
 3 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 98594051d6d5..6cd6ce1fe161 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2115,22 +2115,18 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 }
 
 #ifdef CONFIG_NUMA_BALANCING
-#ifdef CONFIG_SCHED_DEBUG
+__read_mostly bool sched_numa_balancing;
+
 void set_numabalancing_state(bool enabled)
 {
+	sched_numa_balancing = enabled;
+#ifdef CONFIG_SCHED_DEBUG
 	if (enabled)
 		sched_feat_set("NUMA");
 	else
 		sched_feat_set("NO_NUMA");
-}
-#else
-__read_mostly bool sched_numa_balancing;
-
-void set_numabalancing_state(bool enabled)
-{
-	sched_numa_balancing = enabled;
-}
 #endif /* CONFIG_SCHED_DEBUG */
+}
 
 #ifdef CONFIG_PROC_SYSCTL
 int sysctl_numa_balancing(struct ctl_table *table, int write,
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 33d02d6a3cf4..0d5987e8e329 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5525,10 +5525,10 @@ static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
 	unsigned long src_faults, dst_faults;
 	int src_nid, dst_nid;
 
-	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
+	if (!sched_numa_balancing)
 		return -1;
 
-	if (!sched_feat(NUMA))
+	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
 		return -1;
 
 	src_nid = cpu_to_node(env->src_cpu);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 252cfbb78348..fb75db386adc 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1004,14 +1004,8 @@ extern struct static_key sched_feat_keys[__SCHED_FEAT_NR];
 #endif /* SCHED_DEBUG && HAVE_JUMP_LABEL */
 
 #ifdef CONFIG_NUMA_BALANCING
-#define sched_feat_numa(x) sched_feat(x)
-#ifdef CONFIG_SCHED_DEBUG
-#define sched_numa_balancing sched_feat_numa(NUMA)
-#else
 extern bool sched_numa_balancing;
-#endif /* CONFIG_SCHED_DEBUG */
 #else
-#define sched_feat_numa(x) (0)
 #define sched_numa_balancing (0)
 #endif /* CONFIG_NUMA_BALANCING */
 
-- 
2.6.4

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[PATCH 4.3-stable 0/5] Disable automatic numa balancing on UMA Mel Gorman <mgorman@techsingularity.net> - 2016-01-07 19:00 +0100
  [PATCH 2/5] sched/numa: Disable sched_numa_balancing on UMA systems Mel Gorman <mgorman@techsingularity.net> - 2016-01-07 19:00 +0100
  [PATCH 3/5] sched/numa: Remove the NUMA sched_feature Mel Gorman <mgorman@techsingularity.net> - 2016-01-07 19:00 +0100
  [PATCH 4/5] sched/numa: Convert sched_numa_balancing to a static_branch Mel Gorman <mgorman@techsingularity.net> - 2016-01-07 19:10 +0100

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