[PATCH v2 2/3] sched/numa: expose per-task pages-migration-failure

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NUMA balancing will try to migrate pages between nodes, which
could caused by memory policy or numa group aggregation, while
the page migration could failed too for eg when the target node
run out of memory.

Since this is critical to the performance, admin should know
how serious the problem is, and take actions before it causing
too much performance damage, thus this patch expose the counter
as 'migfailed' in '/proc/PID/sched'.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Michal Koutnà <mkoutny@xxxxxxxx>
Suggested-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Michael Wang <yun.wang@xxxxxxxxxxxxxxxxx>
---
 kernel/sched/debug.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index f7e4579e746c..73c4809c8f37 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -848,6 +848,7 @@ static void sched_show_numa(struct task_struct *p, struct seq_file *m)
 	P(total_numa_faults);
 	SEQ_printf(m, "current_node=%d, numa_group_id=%d\n",
 			task_node(p), task_numa_group_id(p));
+	SEQ_printf(m, "migfailed=%lu\n", p->numa_faults_locality[2]);
 	show_numa_stats(p, m);
 	mpol_put(pol);
 #endif
-- 
2.14.4.44.g2045bb6