1 files changed, 84 insertions, 1 deletions

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 06eb6d957c83..6f3c598971fc 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -380,7 +380,7 @@ will be charged as a new owner of it.
 
 5.2 stat file
 
-memory.stat file includes following statistics
+5.2.1 memory.stat file includes following statistics
 
 # per-memory cgroup local status
 cache           - # of bytes of page cache memory.
@@ -438,6 +438,89 @@ Note:
          file_mapped is accounted only when the memory cgroup is owner of page
          cache.)
 
+5.2.2 memory.vmscan_stat
+
+memory.vmscan_stat includes statistics information for memory scanning and
+freeing, reclaiming. The statistics shows memory scanning information since
+memory cgroup creation and can be reset to 0 by writing 0 as
+
+ #echo 0 > ../memory.vmscan_stat
+
+This file contains following statistics.
+
+[param]_[file_or_anon]_pages_by_[reason]_[under_heararchy]
+[param]_elapsed_ns_by_[reason]_[under_hierarchy]
+
+For example,
+
+  scanned_file_pages_by_limit indicates the number of scanned
+  file pages at vmscan.
+
+Now, 3 parameters are supported
+
+  scanned - the number of pages scanned by vmscan
+  rotated - the number of pages activated at vmscan
+  freed   - the number of pages freed by vmscan
+
+If "rotated" is high against scanned/freed, the memcg seems busy.
+
+Now, 2 reason are supported
+
+  limit - the memory cgroup's limit
+  system - global memory pressure + softlimit
+           (global memory pressure not under softlimit is not handled now)
+
+When under_hierarchy is added in the tail, the number indicates the
+total memcg scan of its children and itself.
+
+elapsed_ns is a elapsed time in nanosecond. This may include sleep time
+and not indicates CPU usage. So, please take this as just showing
+latency.
+
+Here is an example.
+
+# cat /cgroup/memory/A/memory.vmscan_stat
+scanned_pages_by_limit 9471864
+scanned_anon_pages_by_limit 6640629
+scanned_file_pages_by_limit 2831235
+rotated_pages_by_limit 4243974
+rotated_anon_pages_by_limit 3971968
+rotated_file_pages_by_limit 272006
+freed_pages_by_limit 2318492
+freed_anon_pages_by_limit 962052
+freed_file_pages_by_limit 1356440
+elapsed_ns_by_limit 351386416101
+scanned_pages_by_system 0
+scanned_anon_pages_by_system 0
+scanned_file_pages_by_system 0
+rotated_pages_by_system 0
+rotated_anon_pages_by_system 0
+rotated_file_pages_by_system 0
+freed_pages_by_system 0
+freed_anon_pages_by_system 0
+freed_file_pages_by_system 0
+elapsed_ns_by_system 0
+scanned_pages_by_limit_under_hierarchy 9471864
+scanned_anon_pages_by_limit_under_hierarchy 6640629
+scanned_file_pages_by_limit_under_hierarchy 2831235
+rotated_pages_by_limit_under_hierarchy 4243974
+rotated_anon_pages_by_limit_under_hierarchy 3971968
+rotated_file_pages_by_limit_under_hierarchy 272006
+freed_pages_by_limit_under_hierarchy 2318492
+freed_anon_pages_by_limit_under_hierarchy 962052
+freed_file_pages_by_limit_under_hierarchy 1356440
+elapsed_ns_by_limit_under_hierarchy 351386416101
+scanned_pages_by_system_under_hierarchy 0
+scanned_anon_pages_by_system_under_hierarchy 0
+scanned_file_pages_by_system_under_hierarchy 0
+rotated_pages_by_system_under_hierarchy 0
+rotated_anon_pages_by_system_under_hierarchy 0
+rotated_file_pages_by_system_under_hierarchy 0
+freed_pages_by_system_under_hierarchy 0
+freed_anon_pages_by_system_under_hierarchy 0
+freed_file_pages_by_system_under_hierarchy 0
+elapsed_ns_by_system_under_hierarchy 0
+
 5.3 swappiness
 
 Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.