memcg: allocate all page_cgroup at boot

Allocate all page_cgroup at boot and remove page_cgroup poitner from
struct page.  This patch adds an interface as

 struct page_cgroup *lookup_page_cgroup(struct page*)

All FLATMEM/DISCONTIGMEM/SPARSEMEM  and MEMORY_HOTPLUG is supported.

Remove page_cgroup pointer reduces the amount of memory by
 - 4 bytes per PAGE_SIZE.
 - 8 bytes per PAGE_SIZE
if memory controller is disabled. (even if configured.)

On usual 8GB x86-32 server, this saves 8MB of NORMAL_ZONE memory.
On my x86-64 server with 48GB of memory, this saves 96MB of memory.
I think this reduction makes sense.

By pre-allocation, kmalloc/kfree in charge/uncharge are removed.
This means
  - we're not necessary to be afraid of kmalloc faiulre.
    (this can happen because of gfp_mask type.)
  - we can avoid calling kmalloc/kfree.
  - we can avoid allocating tons of small objects which can be fragmented.
  - we can know what amount of memory will be used for this extra-lru handling.

I added printk message as

	"allocated %ld bytes of page_cgroup"
        "please try cgroup_disable=memory option if you don't want"

maybe enough informative for users.

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

1 files changed, 13 insertions, 1 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index da2d053a95f1..35a7b5e19465 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -601,8 +601,11 @@ typedef struct pglist_data {
         struct zone node_zones[MAX_NR_ZONES];
         struct zonelist node_zonelists[MAX_ZONELISTS];
         int nr_zones;
-#ifdef CONFIG_FLAT_NODE_MEM_MAP
+#ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */
         struct page *node_mem_map;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+        struct page_cgroup *node_page_cgroup;
+#endif
 #endif
         struct bootmem_data *bdata;
 #ifdef CONFIG_MEMORY_HOTPLUG
@@ -931,6 +934,7 @@ static inline unsigned long early_pfn_to_nid(unsigned long pfn)
 #endif
 
 struct page;
+struct page_cgroup;
 struct mem_section {
         /*
          * This is, logically, a pointer to an array of struct
@@ -948,6 +952,14 @@ struct mem_section {
 
         /* See declaration of similar field in struct zone */
         unsigned long *pageblock_flags;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+        /*
+         * If !SPARSEMEM, pgdat doesn't have page_cgroup pointer. We use
+         * section. (see memcontrol.h/page_cgroup.h about this.)
+         */
+        struct page_cgroup *page_cgroup;
+        unsigned long pad;
+#endif
 };
 
 #ifdef CONFIG_SPARSEMEM_EXTREME