sched/numa: Increment numa_migrate_seq when task runs in correct location

When a task is already running on its preferred node, increment
numa_migrate_seq to indicate that the task is settled if migration is
temporarily disabled, and memory should migrate towards it.

Signed-off-by: Rik van Riel <riel@redhat.com>
[ Only increment migrate_seq if migration temporarily disabled. ]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-35-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f84ac3fb581b..de9b4d8eb853 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1016,8 +1016,16 @@ static void numa_migrate_preferred(struct task_struct *p)
 {
         /* Success if task is already running on preferred CPU */
         p->numa_migrate_retry = 0;
-        if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid)
+        if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid) {
+                /*
+                 * If migration is temporarily disabled due to a task migration
+                 * then re-enable it now as the task is running on its
+                 * preferred node and memory should migrate locally
+                 */
+                if (!p->numa_migrate_seq)
+                        p->numa_migrate_seq++;
                 return;
+        }
 
         /* This task has no NUMA fault statistics yet */
         if (unlikely(p->numa_preferred_nid == -1))