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memcg: Revert "memcg: add memory.vmscan_stat"

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Revert the post-3.0 commit 82f9d486e5 ("memcg: add
memory.vmscan_stat").

The implementation of per-memcg reclaim statistics violates how memcg
hierarchies usually behave: hierarchically.

The reclaim statistics are accounted to child memcgs and the parent
hitting the limit, but not to hierarchy levels in between.  Usually,
hierarchical statistics are perfectly recursive, with each level
representing the sum of itself and all its children.

Since this exports statistics to userspace, this may lead to confusion
and problems with changing things after the release, so revert it now,
we can try again later.

Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Ying Han <yinghan@google.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner
2011-09-14 16:21:58 -07:00
committed by Linus Torvalds
parent a4d3e9e763
commit 185efc0f9a
5 changed files with 18 additions and 303 deletions
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Documentation/cgroups/memory.txt
+1 -84
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@@ -380,7 +380,7 @@ will be charged as a new owner of it.
5.2 stat file
5.2.1 memory.stat file includes following statistics
memory.stat file includes following statistics
# per-memory cgroup local status
cache - # of bytes of page cache memory.
@@ -438,89 +438,6 @@ 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.