memcg: update memcg_test.txt to describe memory thresholds

Decription of sanity check for memory thresholds.

Signed-off-by: Kirill A.  Shutemov <kirill@shutemov.name>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Dan Malek <dan@embeddedalley.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, 21 insertions, 0 deletions

diff --git a/Documentation/cgroups/memcg_test.txt b/Documentation/cgroups/memcg_test.txt
index e01148886b5b..4d32e0ed1917 100644
--- a/Documentation/cgroups/memcg_test.txt
+++ b/Documentation/cgroups/memcg_test.txt
@@ -396,3 +396,24 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
         memory.stat of both A and B.
         See 8.2 of Documentation/cgroups/memory.txt to see what value should be
         written to move_charge_at_immigrate.
+
+ 9.10 Memory thresholds
+        Memory controler implements memory thresholds using cgroups notification
+        API. You can use Documentation/cgroups/cgroup_event_listener.c to test
+        it.
+
+        (Shell-A) Create cgroup and run event listener
+        # mkdir /cgroup/A
+        # ./cgroup_event_listener /cgroup/A/memory.usage_in_bytes 5M
+
+        (Shell-B) Add task to cgroup and try to allocate and free memory
+        # echo $$ >/cgroup/A/tasks
+        # a="$(dd if=/dev/zero bs=1M count=10)"
+        # a=
+
+        You will see message from cgroup_event_listener every time you cross
+        the thresholds.
+
+        Use /cgroup/A/memory.memsw.usage_in_bytes to test memsw thresholds.
+
+        It's good idea to test root cgroup as well.