memcg: convert per-cpu stock from bytes to page granularity

We never keep subpage quantities in the per-cpu stock.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 11 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 09a450684f70..91120a04f935 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1650,14 +1650,14 @@ EXPORT_SYMBOL(mem_cgroup_update_page_stat);
 #define CHARGE_SIZE     (32 * PAGE_SIZE)
 struct memcg_stock_pcp {
         struct mem_cgroup *cached; /* this never be root cgroup */
-        int charge;
+        unsigned int nr_pages;
         struct work_struct work;
 };
 static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
 static atomic_t memcg_drain_count;
 
 /*
- * Try to consume stocked charge on this cpu. If success, PAGE_SIZE is consumed
+ * 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.
@@ -1668,8 +1668,8 @@ static bool consume_stock(struct mem_cgroup *mem)
         bool ret = true;
 
         stock = &get_cpu_var(memcg_stock);
-        if (mem == stock->cached && stock->charge)
-                stock->charge -= PAGE_SIZE;
+        if (mem == stock->cached && stock->nr_pages)
+                stock->nr_pages--;
         else /* need to call res_counter_charge */
                 ret = false;
         put_cpu_var(memcg_stock);
@@ -1683,13 +1683,15 @@ static void drain_stock(struct memcg_stock_pcp *stock)
 {
         struct mem_cgroup *old = stock->cached;
 
-        if (stock->charge) {
-                res_counter_uncharge(&old->res, stock->charge);
+        if (stock->nr_pages) {
+                unsigned long bytes = stock->nr_pages * PAGE_SIZE;
+
+                res_counter_uncharge(&old->res, bytes);
                 if (do_swap_account)
-                        res_counter_uncharge(&old->memsw, stock->charge);
+                        res_counter_uncharge(&old->memsw, bytes);
+                stock->nr_pages = 0;
         }
         stock->cached = NULL;
-        stock->charge = 0;
 }
 
 /*
@@ -1706,7 +1708,7 @@ static void drain_local_stock(struct work_struct *dummy)
  * Cache charges(val) which is from res_counter, to local per_cpu area.
  * This will be consumed by consume_stock() function, later.
  */
-static void refill_stock(struct mem_cgroup *mem, int val)
+static void refill_stock(struct mem_cgroup *mem, unsigned int nr_pages)
 {
         struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);
 
@@ -1714,7 +1716,7 @@ static void refill_stock(struct mem_cgroup *mem, int val)
                 drain_stock(stock);
                 stock->cached = mem;
         }
-        stock->charge += val;
+        stock->nr_pages += nr_pages;
         put_cpu_var(memcg_stock);
 }
 
@@ -2012,7 +2014,7 @@ again:
         } while (ret != CHARGE_OK);
 
         if (csize > page_size)
-                refill_stock(mem, csize - page_size);
+                refill_stock(mem, (csize - page_size) >> PAGE_SHIFT);
         css_put(&mem->css);
 done:
         *memcg = mem;