memcg: swappiness

Currently, /proc/sys/vm/swappiness can change swappiness ratio for global
reclaim.  However, memcg reclaim doesn't have tuning parameter for itself.

In general, the optimal swappiness depend on workload.  (e.g.  hpc
workload need to low swappiness than the others.)

Then, per cgroup swappiness improve administrator tunability.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/controllers/memory.txt b/Documentation/controllers/memory.txt
index d71745cc2f00..e1501964df1e 100644
--- a/Documentation/controllers/memory.txt
+++ b/Documentation/controllers/memory.txt
@@ -314,6 +314,15 @@ will be charged as a new owner of it.
         showing for better debug please see the code for meanings.
 
 
+5.3 swappiness
+  Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
+
+  Following cgroup's swapiness can't be changed.
+  - root cgroup (uses /proc/sys/vm/swappiness).
+  - a cgroup which uses hierarchy and it has child cgroup.
+  - a cgroup which uses hierarchy and not the root of hierarchy.
+
+
 6. Hierarchy support
 
 The memory controller supports a deep hierarchy and hierarchical accounting.