linux-stable.git/Documentation/cgroups/memory.txt, branch v3.2.83

memcg: oom: fix totalpages calculation for memory.swappiness==0

2012-12-06T11:20:08+00:00

commit 9a5a8f19b43430752067ecaee62fc59e11e88fa6 upstream.

oom_badness() takes a totalpages argument which says how many pages are
available and it uses it as a base for the score calculation.  The value
is calculated by mem_cgroup_get_limit which considers both limit and
total_swap_pages (resp.  memsw portion of it).

This is usually correct but since fe35004fbf9e ("mm: avoid swapping out
with swappiness==0") we do not swap when swappiness is 0 which means
that we cannot really use up all the totalpages pages.  This in turn
confuses oom score calculation if the memcg limit is much smaller than
the available swap because the used memory (capped by the limit) is
negligible comparing to totalpages so the resulting score is too small
if adj!=0 (typically task with CAP_SYS_ADMIN or non zero oom_score_adj).
A wrong process might be selected as result.

The problem can be worked around by checking mem_cgroup_swappiness==0
and not considering swap at all in such a case.

Signed-off-by: Michal Hocko 
Acked-by: David Rientjes 
Acked-by: Johannes Weiner 
Acked-by: KOSAKI Motohiro 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

memcg: skip scanning active lists based on individual size

2011-11-02T23:07:00+00:00

Reclaim decides to skip scanning an active list when the corresponding
inactive list is above a certain size in comparison to leave the assumed
working set alone while there are still enough reclaim candidates around.

The memcg implementation of comparing those lists instead reports whether
the whole memcg is low on the requested type of inactive pages,
considering all nodes and zones.

This can lead to an oversized active list not being scanned because of the
state of the other lists in the memcg, as well as an active list being
scanned while its corresponding inactive list has enough pages.

Not only is this wrong, it's also a scalability hazard, because the global
memory state over all nodes and zones has to be gathered for each memcg
and zone scanned.

Make these calculations purely based on the size of the two LRU lists
that are actually affected by the outcome of the decision.

Signed-off-by: Johannes Weiner 
Reviewed-by: Rik van Riel 
Cc: KOSAKI Motohiro 
Acked-by: KAMEZAWA Hiroyuki 
Cc: Daisuke Nishimura 
Cc: Balbir Singh 
Reviewed-by: Minchan Kim 
Reviewed-by: Ying Han 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: Revert "memcg: add memory.vmscan_stat"

2011-09-15T01:09:38+00:00

Revert the post-3.0 commit 82f9d486e59f5 ("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 
Acked-by: KAMEZAWA Hiroyuki 
Cc: Daisuke Nishimura 
Cc: Michal Hocko 
Cc: Ying Han 
Cc: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: add memory.vmscan_stat

2011-07-26T23:49:42+00:00

The commit log of 0ae5e89c60c9 ("memcg: count the soft_limit reclaim
in...") says it adds scanning stats to memory.stat file.  But it doesn't
because we considered we needed to make a concensus for such new APIs.

This patch is a trial to add memory.scan_stat. This shows
  - the number of scanned pages(total, anon, file)
  - the number of rotated pages(total, anon, file)
  - the number of freed pages(total, anon, file)
  - the number of elaplsed time (including sleep/pause time)

  for both of direct/soft reclaim.

The biggest difference with oringinal Ying's one is that this file
can be reset by some write, as

  # echo 0 ...../memory.scan_stat

Example of output is here. This is a result after make -j 6 kernel
under 300M limit.

  [kamezawa@bluextal ~]$ cat /cgroup/memory/A/memory.scan_stat
  [kamezawa@bluextal ~]$ 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

total_xxxx is for hierarchy management.

This will be useful for further memcg developments and need to be
developped before we do some complicated rework on LRU/softlimit
management.

This patch adds a new struct memcg_scanrecord into scan_control struct.
sc->nr_scanned at el is not designed for exporting information.  For
example, nr_scanned is reset frequentrly and incremented +2 at scanning
mapped pages.

To avoid complexity, I added a new param in scan_control which is for
exporting scanning score.

Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Daisuke Nishimura 
Cc: Michal Hocko 
Cc: Ying Han 
Cc: Andrew Bresticker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation: fix cgroup typos and formatting

2011-06-16T04:52:50+00:00

Fix format and spelling.

Signed-off-by: Jörg Sommer 
Acked-by: Paul Menage 
Signed-off-by: Randy Dunlap 
Signed-off-by: Linus Torvalds

Documentation: update cgroupfs mount point

2011-06-16T04:52:50+00:00

According to commit 676db4af0430 ("cgroupfs: create /sys/fs/cgroup to
mount cgroupfs on") the canonical mountpoint for the cgroup filesystem
is /sys/fs/cgroup.  Hence, this should be used in the documentation.

Signed-off-by: Jörg Sommer 
Acked-by: Paul Menage 
Signed-off-by: Randy Dunlap 
Signed-off-by: Linus Torvalds

memcg: add documentation for the memory.numastat API

2011-06-16T03:03:59+00:00

[akpm@linux-foundation.org: rework text, fit it into 80-cols]
Signed-off-by: Ying Han 
Reviewed-by: KOSAKI Motohiro 
Acked-by: Balbir Singh 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: update documentation to describe usage_in_bytes

2011-04-28T18:28:21+00:00

Since 569b846d ("memcg: coalesce uncharge during unmap/truncate"), we do
batched (delayed) uncharge at truncation/unmap.  And since cdec2e42(memcg:
coalesce charging via percpu storage), we have percpu cache for
res_counter.

These changes improved performance of memory cgroup very much, but made
res_counter->usage usually have a bigger value than the actual value of
memory usage.  So, *.usage_in_bytes, which show res_counter->usage, are
not desirable for precise values of memory(and swap) usage anymore.

Instead of removing these files completely(because we cannot know
res_counter->usage without them), this patch updates the meaning of those
files.

Signed-off-by: Daisuke Nishimura 
Acked-by: KAMEZAWA Hiroyuki 
Acked-by: Michal Hocko 
Cc: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: clarify use_hierarchy documentation

2011-02-17T08:17:21+00:00

The memcg code does not allow changing memory.use_hierarchy if the
parent cgroup has enabled use_hierarchy.  Update documentation to match
the code.

Signed-off-by: Greg Thelen 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Jiri Kosina

memcg: update documentation

2010-05-27T16:12:43+00:00

Some information are old, and I think current document doesn't work as "a
guide for users".  We need summary of all of our controls, at least.

Signed-off-by: KAMEZAWA Hiroyuki 
Reviewed-by: Randy Dunlap 
Cc: Balbir Singh 
Cc: Daisuke Nishimura 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds