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>
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 23d1262..ab0a021 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -179,6 +179,9 @@
pages that are selected for reclaiming come from the per cgroup LRU
list.
+NOTE: Reclaim does not work for the root cgroup, since we cannot set any
+limits on the root cgroup.
+
2. Locking
The memory controller uses the following hierarchy
@@ -210,6 +213,7 @@
NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
mega or gigabytes.
NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited).
+NOTE: We cannot set limits on the root cgroup any more.
# cat /cgroups/0/memory.limit_in_bytes
4194304