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>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2656af0..ca665f8 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 */