[PATCH 01/11] memcg: Make it possible to use the stock for more than one page.

[Glauber Costa <glommer@parallels.com>]

From: Suleiman Souhlal <ssouhlal@FreeBSD.org>

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Glauber Costa <glommer@parallels.com>
Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |   21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f72b5e5..9304db2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1967,19 +1967,22 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
 static DEFINE_MUTEX(percpu_charge_mutex);
 
 /*
- * Try to consume stocked charge on this cpu. If success, one page is consumed
- * from local stock and true is returned. If the stock is 0 or charges from a
- * cgroup which is not current target, returns false. This stock will be
- * refilled.
+ * Try to consume stocked charge on this cpu. If success, nr_pages pages are
+ * consumed from local stock and true is returned. If the stock is 0 or
+ * charges from a cgroup which is not current target, returns false.
+ * This stock will be refilled.
  */
-static bool consume_stock(struct mem_cgroup *memcg)
+static bool consume_stock(struct mem_cgroup *memcg, int nr_pages)
 {
 	struct memcg_stock_pcp *stock;
 	bool ret = true;
 
+	if (nr_pages > CHARGE_BATCH)
+		return false;
+
 	stock = &get_cpu_var(memcg_stock);
-	if (memcg == stock->cached && stock->nr_pages)
-		stock->nr_pages--;
+	if (memcg == stock->cached && stock->nr_pages >= nr_pages)
+		stock->nr_pages -= nr_pages;
 	else /* need to call res_counter_charge */
 		ret = false;
 	put_cpu_var(memcg_stock);
@@ -2278,7 +2281,7 @@ again:
 		VM_BUG_ON(css_is_removed(&memcg->css));
 		if (mem_cgroup_is_root(memcg))
 			goto done;
-		if (nr_pages == 1 && consume_stock(memcg))
+		if (consume_stock(memcg, nr_pages))
 			goto done;
 		css_get(&memcg->css);
 	} else {
@@ -2303,7 +2306,7 @@ again:
 			rcu_read_unlock();
 			goto done;
 		}
-		if (nr_pages == 1 && consume_stock(memcg)) {
+		if (consume_stock(memcg, nr_pages)) {
 			/*
 			 * It seems dagerous to access memcg without css_get().
 			 * But considering how consume_stok works, it's not
-- 
1.7.10.2