From: Rik van Riel <r...@redhat.com>

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.

[mgor...@suse.de: Only increment migrate_seq if migration temporarily disabled]
Signed-off-by: Rik van Riel <r...@redhat.com>
---
 kernel/sched/fair.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 559175b..9a2e68e 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))
-- 
1.8.4

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