Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sameo/mfd-2.6

[mv-sheeva.git] / Documentation / cgroups / memcg_test.txt

diff --git a/Documentation/cgroups/memcg_test.txt b/Documentation/cgroups/memcg_test.txt
index 19533f93b7a2ac4175142947142569199dacc51f..f7f68b2ac1990058b03f078019083d9865b36773 100644 (file)
--- a/Documentation/cgroups/memcg_test.txt
+++ b/Documentation/cgroups/memcg_test.txt
@@ -1,6 +1,6 @@
 Memory Resource Controller(Memcg)  Implementation Memo.
-Last Updated: 2008/12/15
-Base Kernel Version: based on 2.6.28-rc8-mm.
+Last Updated: 2010/2
+Base Kernel Version: based on 2.6.33-rc7-mm(candidate for 34).
 
 Because VM is getting complex (one of reasons is memcg...), memcg's behavior
 is complex. This is a document for memcg's internal behavior.
@@ -337,6 +337,83 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
        race and lock dependency with other cgroup subsystems.
 
        example)
-       # mount -t cgroup none /cgroup -t cpuset,memory,cpu,devices
+       # mount -t cgroup none /cgroup -o cpuset,memory,cpu,devices
 
        and do task move, mkdir, rmdir etc...under this.
+
+ 9.7 swapoff.
+       Besides management of swap is one of complicated parts of memcg,
+       call path of swap-in at swapoff is not same as usual swap-in path..
+       It's worth to be tested explicitly.
+
+       For example, test like following is good.
+       (Shell-A)
+       # mount -t cgroup none /cgroup -o memory
+       # mkdir /cgroup/test
+       # echo 40M > /cgroup/test/memory.limit_in_bytes
+       # echo 0 > /cgroup/test/tasks
+       Run malloc(100M) program under this. You'll see 60M of swaps.
+       (Shell-B)
+       # move all tasks in /cgroup/test to /cgroup
+       # /sbin/swapoff -a
+       # rmdir /cgroup/test
+       # kill malloc task.
+
+       Of course, tmpfs v.s. swapoff test should be tested, too.
+
+ 9.8 OOM-Killer
+       Out-of-memory caused by memcg's limit will kill tasks under
+       the memcg. When hierarchy is used, a task under hierarchy
+       will be killed by the kernel.
+       In this case, panic_on_oom shouldn't be invoked and tasks
+       in other groups shouldn't be killed.
+
+       It's not difficult to cause OOM under memcg as following.
+       Case A) when you can swapoff
+       #swapoff -a
+       #echo 50M > /memory.limit_in_bytes
+       run 51M of malloc
+
+       Case B) when you use mem+swap limitation.
+       #echo 50M > memory.limit_in_bytes
+       #echo 50M > memory.memsw.limit_in_bytes
+       run 51M of malloc
+
+ 9.9 Move charges at task migration
+       Charges associated with a task can be moved along with task migration.
+
+       (Shell-A)
+       #mkdir /cgroup/A
+       #echo $$ >/cgroup/A/tasks
+       run some programs which uses some amount of memory in /cgroup/A.
+
+       (Shell-B)
+       #mkdir /cgroup/B
+       #echo 1 >/cgroup/B/memory.move_charge_at_immigrate
+       #echo "pid of the program running in group A" >/cgroup/B/tasks
+
+       You can see charges have been moved by reading *.usage_in_bytes or
+       memory.stat of both A and B.
+       See 8.2 of Documentation/cgroups/memory.txt to see what value should be
+       written to move_charge_at_immigrate.
+
+ 9.10 Memory thresholds
+       Memory controler implements memory thresholds using cgroups notification
+       API. You can use Documentation/cgroups/cgroup_event_listener.c to test
+       it.
+
+       (Shell-A) Create cgroup and run event listener
+       # mkdir /cgroup/A
+       # ./cgroup_event_listener /cgroup/A/memory.usage_in_bytes 5M
+
+       (Shell-B) Add task to cgroup and try to allocate and free memory
+       # echo $$ >/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.