memcg: remove the overhead associated with the root cgroup

Change the memory cgroup to remove the overhead associated with accounting
all pages in the root cgroup.  As a side-effect, we can no longer set a
memory hard limit in the root cgroup.

A new flag to track whether the page has been accounted or not has been
added as well.  Flags are now set atomically for page_cgroup,
pcg_default_flags is now obsolete and removed.

[akpm@linux-foundation.org: fix a few documentation glitches]
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index ada779f24178..4b938d4f3ac2 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -38,6 +38,7 @@ enum {
         PCG_LOCK,  /* page cgroup is locked */
         PCG_CACHE, /* charged as cache */
         PCG_USED, /* this object is in use. */
+        PCG_ACCT_LRU, /* page has been accounted for */
 };
 
 #define TESTPCGFLAG(uname, lname)                       \
@@ -52,11 +53,23 @@ static inline void SetPageCgroup##uname(struct page_cgroup *pc)\
 static inline void ClearPageCgroup##uname(struct page_cgroup *pc)       \
         { clear_bit(PCG_##lname, &pc->flags);  }
 
+#define TESTCLEARPCGFLAG(uname, lname)                  \
+static inline int TestClearPageCgroup##uname(struct page_cgroup *pc)    \
+        { return test_and_clear_bit(PCG_##lname, &pc->flags);  }
+
 /* Cache flag is set only once (at allocation) */
 TESTPCGFLAG(Cache, CACHE)
+CLEARPCGFLAG(Cache, CACHE)
+SETPCGFLAG(Cache, CACHE)
 
 TESTPCGFLAG(Used, USED)
 CLEARPCGFLAG(Used, USED)
+SETPCGFLAG(Used, USED)
+
+SETPCGFLAG(AcctLRU, ACCT_LRU)
+CLEARPCGFLAG(AcctLRU, ACCT_LRU)
+TESTPCGFLAG(AcctLRU, ACCT_LRU)
+TESTCLEARPCGFLAG(AcctLRU, ACCT_LRU)
 
 static inline int page_cgroup_nid(struct page_cgroup *pc)
 {