linux-stable.git/Documentation/cgroups/memory.txt, branch v3.7

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

2012-11-16T22:33:04+00:00

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 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: trivial fixes for Documentation/cgroups/memory.txt

2012-10-09T07:22:54+00:00

While reading through Documentation/cgroups/memory.txt, I found a number
of minor wordos and typos.  The patch below is a conservative handling of
some of these: it provides just a number of "obviously correct" fixes to
the English that improve the readability of the document somewhat.
Obviously some more significant fixes need to be made to the document, but
some of those may not be in the "obvious correct" category.

Signed-off-by: Michael Kerrisk 
Acked-by: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memcg: complete documentation for tcp memcg files

2012-08-01T01:42:43+00:00

Signed-off-by: Wanpeng Li 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: rename config variables

2012-08-01T01:42:43+00:00

Sanity:

CONFIG_CGROUP_MEM_RES_CTLR -> CONFIG_MEMCG
CONFIG_CGROUP_MEM_RES_CTLR_SWAP -> CONFIG_MEMCG_SWAP
CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED -> CONFIG_MEMCG_SWAP_ENABLED
CONFIG_CGROUP_MEM_RES_CTLR_KMEM -> CONFIG_MEMCG_KMEM

[mhocko@suse.cz: fix missed bits]
Cc: Glauber Costa 
Acked-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: KAMEZAWA Hiroyuki 
Cc: Hugh Dickins 
Cc: Tejun Heo 
Cc: Aneesh Kumar K.V 
Cc: David Rientjes 
Cc: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: move charges to root cgroup if use_hierarchy=0

2012-05-29T23:22:27+00:00

Presently, at removal of cgroup, ->pre_destroy() is called and moves
charges to the parent cgroup.  A major reason for returning -EBUSY from
->pre_destroy() is that the 'moving' hits the parent's resource
limitation.  It happens only when use_hierarchy=0.

Considering use_hierarchy=0, all cgroups should be flat.  So, no one
cannot justify moving charges to parent...parent and children are in flat
configuration, not hierarchical.

This patch modifes the code to move charges to the root cgroup at
rmdir/force_empty if use_hierarchy==0.  This will much simplify rmdir()
and reduce error in ->pre_destroy.

Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Aneesh Kumar K.V 
Cc: Michal Hocko 
Cc: Johannes Weiner 
Cc: Frederic Weisbecker 
Cc: Ying Han 
Cc: Glauber Costa 
Reviewed-by: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: fix/change behavior of shared anon at moving task

2012-05-29T23:22:24+00:00

This patch changes memcg's behavior at task_move().

At task_move(), the kernel scans a task's page table and move the changes
for mapped pages from source cgroup to target cgroup.  There has been a
bug at handling shared anonymous pages for a long time.

Before patch:
  - The spec says 'shared anonymous pages are not moved.'
  - The implementation was 'shared anonymoys pages may be moved'.
    If page_mapcount <=2, shared anonymous pages's charge were moved.

After patch:
  - The spec says 'all anonymous pages are moved'.
  - The implementation is 'all anonymous pages are moved'.

Considering usage of memcg, this will not affect user's experience.
'shared anonymous' pages only exists between a tree of processes which
don't do exec().  Moving one of process without exec() seems not sane.
For example, libcgroup will not be affected by this change.  (Anyway, no
one noticed the implementation for a long time...)

Below is a discussion log:

 - current spec/implementation are complex
 - Now, shared file caches are moved
 - It adds unclear check as page_mapcount(). To do correct check,
   we should check swap users, etc.
 - No one notice this implementation behavior. So, no one get benefit
   from the design.
 - In general, once task is moved to a cgroup for running, it will not
   be moved....
 - Finally, we have control knob as memory.move_charge_at_immigrate.

Here is a patch to allow moving shared pages, completely. This makes
memcg simpler and fix current broken code.

Suggested-by: Hugh Dickins 
Signed-off-by: KAMEZAWA Hiroyuki 
Acked-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: Naoya Horiguchi 
Cc: Glauber Costa 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation: memcg: future proof hierarchical statistics documentation

2012-05-29T23:22:20+00:00

The hierarchical versions of per-memcg counters in memory.stat are all
calculated the same way and are all named total_.

Documenting the pattern is easier for maintenance than listing each
counter twice.

Signed-off-by: Johannes Weiner 
Acked-by: Michal Hocko 
Acked-by: KOSAKI Motohiro 
Acked-by: Ying Han 
Randy Dunlap 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: fix up documentation on global LRU

2012-04-12T20:12:11+00:00

In v3.3-rc1, the global LRU was removed in commit 925b7673cce3 ("mm:
make per-memcg LRU lists exclusive").  The patch fixes up the memcg
docs.

I left the swap session to someone who has better understanding of
'memory+swap'.

Signed-off-by: Ying Han 
Acked-by: Michal Hocko 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: fix pgpgin/pgpgout documentation

2012-01-13T04:13:06+00:00

The two memcg stats pgpgin/pgpgout have different meaning than the ones
in vmstat, which indicates that we picked a bad naming for them.

It might be late to change the stat name, but better documentation is
always helpful.

Signed-off-by: Ying Han 
Acked-by: KAMEZAWA Hiroyuki 
Acked-by: Johannes Weiner 
Acked-by: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation/cgroups/memory.txt: fix typo

2012-01-13T04:13:06+00:00

It should be memsw.max_usage_in_bytes. This typo has been there for
a really long time.

Signed-off-by: Zhu Yanhai 
Acked-by: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds