[PATCH] mm/vmstat.c: erase latency in vmstat_shepherd

From: Jiang Biao <redacted>

Many 100us+ latencies have been deteceted in vmstat_shepherd()
on CPX platform which has 208 logic cpus. And vmstat_shepherd is
queued every second, which could make the case worse.

Add schedule point in vmstat_shepherd() to erase the latency.

Signed-off-by: Jiang Biao <redacted>
Reported-by: Bin Lai <redacted>
---
 mm/vmstat.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index f8942160fc95..b538199883b5 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c

@@ -1953,6 +1953,8 @@ static void vmstat_shepherd(struct work_struct *w)
 
 		if (!delayed_work_pending(dw) && need_update(cpu))
 			queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0);
+
+		cond_resched();
 	}
 	put_online_cpus();
 

-- 
2.21.0