[PATCH] mm/vmstat: stagger per-cpu vmstat updates to avoid zone->lock contention

[Dmitry Ilvokhin]

Fix by spreading the shepherd's initial wakeup across the stat plain
sysctl_stat_interval to preserve the stagger. Every CPU still fires once
per interval, same frequency, different phase.

Signed-off-by: Dmitry Ilvokhin <d@xxxxxxxxxxxx>
---
 mm/vmstat.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 2370c6fb1fcd..aee99786718a 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -2042,7 +2042,7 @@ static void vmstat_update(struct work_struct *w)
 		 */
 		queue_delayed_work_on(smp_processor_id(), mm_percpu_wq,
 				this_cpu_ptr(&vmstat_work),
-				round_jiffies_relative(sysctl_stat_interval));
+				sysctl_stat_interval);
 	}
 }
 
@@ -2140,7 +2140,8 @@ static void vmstat_shepherd(struct work_struct *w)
 				continue;
 
 			if (!delayed_work_pending(dw) && need_update(cpu))
-				queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0);
+				queue_delayed_work_on(cpu, mm_percpu_wq, dw,
+					(sysctl_stat_interval * cpu) / nr_cpu_ids);
 		}
 
 		cond_resched();
-- 
2.52.0