Memory Resource Controller(Memcg) Implementation Memo.
-Last Updated: 2009/1/20
-Base Kernel Version: based on 2.6.29-rc2.
+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.
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.
For example, test like following is good.
(Shell-A)
- # mount -t cgroup none /cgroup -t memory
+ # mount -t cgroup none /cgroup -o memory
# mkdir /cgroup/test
# echo 40M > /cgroup/test/memory.limit_in_bytes
# echo 0 > /cgroup/test/tasks
#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.