[PATCH] mm: memcontrol: optimize per-lruvec stats counter memory usage

[Muchun Song]

The vmstat threshold is 32 (MEMCG_CHARGE_BATCH), so the type of s32
of lruvec_stat_cpu is enough. And introduce struct per_cpu_lruvec_stat
to optimize memory usage.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 include/linux/memcontrol.h | 6 +++++-
 mm/memcontrol.c            | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index f9a496c4eac7..34cf119976b1 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -92,6 +92,10 @@ struct lruvec_stat {
 	long count[NR_VM_NODE_STAT_ITEMS];
 };
 
+struct per_cpu_lruvec_stat {
+	s32 count[NR_VM_NODE_STAT_ITEMS];
+};
+
 /*
  * Bitmap of shrinker::id corresponding to memcg-aware shrinkers,
  * which have elements charged to this memcg.
@@ -111,7 +115,7 @@ struct mem_cgroup_per_node {
 	struct lruvec_stat __percpu *lruvec_stat_local;
 
 	/* Subtree VM stats (batched updates) */
-	struct lruvec_stat __percpu *lruvec_stat_cpu;
+	struct per_cpu_lruvec_stat __percpu *lruvec_stat_cpu;
 	atomic_long_t		lruvec_stat[NR_VM_NODE_STAT_ITEMS];
 
 	unsigned long		lru_zone_size[MAX_NR_ZONES][NR_LRU_LISTS];
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 49fbcf003bf5..c874ea37b05d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5184,7 +5184,7 @@ static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
 		return 1;
 	}
 
-	pn->lruvec_stat_cpu = alloc_percpu_gfp(struct lruvec_stat,
+	pn->lruvec_stat_cpu = alloc_percpu_gfp(struct per_cpu_lruvec_stat,
 					       GFP_KERNEL_ACCOUNT);
 	if (!pn->lruvec_stat_cpu) {
 		free_percpu(pn->lruvec_stat_local);
-- 
2.11.0