[RFC][PATCH 1/3] memcg: documentation for controll file

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

Add a documentation for memory resource controller's files.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


Index: mm-2.6.26-rc2-mm1/Documentation/controllers/memory_files.txt
===================================================================
--- /dev/null
+++ mm-2.6.26-rc2-mm1/Documentation/controllers/memory_files.txt
@@ -0,0 +1,76 @@
+Files under memory resource controller and its resource counter.
+(See controllers/memory.txt about memory resource controller)
+
+* memory.usage_in_bytes
+  (read)
+  Currently accounted memory usage under memory controller in bytes.
+  multiple of PAGE_SIZE.
+
+  Even if there is no tasks under controller, some page caches and
+  swap caches are still accounted. (See memory.force_empty below.)
+
+  (write)
+  no write operation
+
+* memory.limit_in_bytes
+  (read)
+  Current limit of usage to this memory resource controller in bytes.
+  (write)
+  Set limit to this memory resource controller.
+  A user can use "K', 'M', 'G' to specify the limit.
+
+  (Example) You can set limit of 400M by following.
+  % echo 400M > /path to cgroup/memory.limit_in_bytes
+
+* memory.max_usage_in_bytes
+  (read)
+  Recorded maximum memory usage under this memory controller.
+
+  (write)
+  Reset the record to 0.
+
+  (example usage)
+  1. create a cgroup
+  % mkdir /path_to_cgroup/my_cgroup.
+
+  2. enter the cgroup
+  % echo $$ > /path_to_cgroup/my_cgroup/tasks.
+
+  3. Run your program
+  % Run......
+
+  4. See how much you used.
+  % cat /path_to_cgroup/my_cgroup/memory.max_usage_in_bytes.
+
+  Now you know how much your application will use. Maybe this
+  can be a good to set  limits_in_bytes to some proper value.
+
+* memory.force_empty
+  (read)
+  not allowed.
+  (write)
+  Drop all charges under cgroup. This can be called only when
+  there is no task under this cgroup. This is here for debug purpose.
+
+* memory.stat
+  (read)
+  show 6 values. (will change in future)
+  cache          .... usage accounted as File-Cache.
+  anon/swapcache .... usage accounted as anonymous memory or swapcache.
+  pgpgin         .... # of page-in under this cgroup.
+  pgpgout        .... # of page-out under this cgroup
+  active         .... amounts of memory which is treated as 'active' 
+  inactive       .... amounts of memory which is treated as 'inactive'
+  (write)
+  not allowed 
+
+* memory.failcnt
+  (read)
+  The number of blocked memory allocation.
+  Until the usage reaches the limit, memory allocation is not blocked.
+  When it reaches, memory allocation is blocked and try to reclaim memory
+  from LRU.
+
+  (write)
+  Reset to 0.
+

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