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Subject[tip:sched/core] sched/numa: Disable sched_numa_balancing on UMA systems
Commit-ID:  c3b9bc5bbfc3750570d788afffd431263ef695c6
Gitweb: http://git.kernel.org/tip/c3b9bc5bbfc3750570d788afffd431263ef695c6
Author: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
AuthorDate: Tue, 11 Aug 2015 16:30:12 +0530
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 13 Sep 2015 09:52:53 +0200

sched/numa: Disable sched_numa_balancing on UMA systems

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>
---
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 2656af0..ca665f8 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 3a6ac55..e8f0828 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5562,10 +5562,10 @@ 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 d0b303d..0d8f885 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 */


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