sched/numa: Always try to migrate to preferred node at task_numa_placement() time

It is possible that at task_numa_placement() time, the task's
numa_preferred_nid does not change, but the task is not
actually running on the preferred node at the time.

In that case, we still want to attempt migration to the
preferred node.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: mgorman@suse.de
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140604163315.1dbc7b56@cuia.bos.redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8fbb0116bb5a..3fa3e1839c86 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1613,11 +1613,13 @@ static void task_numa_placement(struct task_struct *p)
                 spin_unlock_irq(group_lock);
         }
 
-        /* Preferred node as the node with the most faults */
-        if (max_faults && max_nid != p->numa_preferred_nid) {
-                /* Update the preferred nid and migrate task if possible */
-                sched_setnuma(p, max_nid);
-                numa_migrate_preferred(p);
+        if (max_faults) {
+                /* Set the new preferred node */
+                if (max_nid != p->numa_preferred_nid)
+                        sched_setnuma(p, max_nid);
+
+                if (task_node(p) != p->numa_preferred_nid)
+                        numa_migrate_preferred(p);
         }
 }