memcg: convert uncharge batching from bytes to page granularity

We never uncharge subpage quantities.

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>

2 files changed, 12 insertions, 10 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4b601be3dace..98fc7ed4b191 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1524,8 +1524,8 @@ struct task_struct {
         struct memcg_batch_info {
                 int do_batch;   /* incremented when batch uncharge started */
                 struct mem_cgroup *memcg; /* target memcg of uncharge */
-                unsigned long bytes;            /* uncharged usage */
-                unsigned long memsw_bytes; /* uncharged mem+swap usage */
+                unsigned long nr_pages; /* uncharged usage */
+                unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
         } memcg_batch;
 #endif
 };
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 91120a04f935..9dfbed2aacc9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2579,9 +2579,9 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype,
         if (batch->memcg != mem)
                 goto direct_uncharge;
         /* remember freed charge and uncharge it later */
-        batch->bytes += PAGE_SIZE;
+        batch->nr_pages++;
         if (uncharge_memsw)
-                batch->memsw_bytes += PAGE_SIZE;
+                batch->memsw_nr_pages++;
         return;
 direct_uncharge:
         res_counter_uncharge(&mem->res, page_size);
@@ -2708,8 +2708,8 @@ void mem_cgroup_uncharge_start(void)
         /* We can do nest. */
         if (current->memcg_batch.do_batch == 1) {
                 current->memcg_batch.memcg = NULL;
-                current->memcg_batch.bytes = 0;
-                current->memcg_batch.memsw_bytes = 0;
+                current->memcg_batch.nr_pages = 0;
+                current->memcg_batch.memsw_nr_pages = 0;
         }
 }
 
@@ -2730,10 +2730,12 @@ void mem_cgroup_uncharge_end(void)
          * This "batch->memcg" is valid without any css_get/put etc...
          * bacause we hide charges behind us.
          */
-        if (batch->bytes)
-                res_counter_uncharge(&batch->memcg->res, batch->bytes);
-        if (batch->memsw_bytes)
-                res_counter_uncharge(&batch->memcg->memsw, batch->memsw_bytes);
+        if (batch->nr_pages)
+                res_counter_uncharge(&batch->memcg->res,
+                                     batch->nr_pages * PAGE_SIZE);
+        if (batch->memsw_nr_pages)
+                res_counter_uncharge(&batch->memcg->memsw,
+                                     batch->memsw_nr_pages * PAGE_SIZE);
         memcg_oom_recover(batch->memcg);
         /* forget this pointer (for sanity check) */
         batch->memcg = NULL;