linux.git/Documentation/cgroups/memory.txt, branch v2.6.37

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

memcg: move charge of file pages

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

This patch adds support for moving charge of file pages, which include
normal file, tmpfs file and swaps of tmpfs file.  It's enabled by setting
bit 1 of /memory.move_charge_at_immigrate.

Unlike the case of anonymous pages, file pages(and swaps) in the range
mmapped by the task will be moved even if the task hasn't done page fault,
i.e.  they might not be the task's "RSS", but other task's "RSS" that maps
the same file.  And mapcount of the page is ignored(the page can be moved
even if page_mapcount(page) > 1).  So, conditions that the page/swap
should be met to be moved is that it must be in the range mmapped by the
target task and it must be charged to the old cgroup.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix warning]
Signed-off-by: Daisuke Nishimura 
Acked-by: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: oom kill disable and oom status

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

This adds a feature to disable oom-killer for memcg, if disabled, of
course, tasks under memcg will stop.

But now, we have oom-notifier for memcg.  And the world around memcg is
not under out-of-memory.  memcg's out-of-memory just shows memcg hits
limit.  Then, administrator or management daemon can recover the situation
by

	- kill some process
	- enlarge limit, add more swap.
	- migrate some tasks
	- remove file cache on tmps (difficult ?)

Unlike oom-killer, you can take enough information before killing tasks.
(by gcore, or, ps etc.)

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Daisuke Nishimura 
Cc: Balbir Singh 
Cc: Daisuke Nishimura 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: oom notifier

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

Considering containers or other resource management softwares in userland,
event notification of OOM in memcg should be implemented.  Now, memcg has
"threshold" notifier which uses eventfd, we can make use of it for oom
notification.

This patch adds oom notification eventfd callback for memcg.  The usage is
very similar to threshold notifier, but control file is memory.oom_control
and no arguments other than eventfd is required.

	% cgroup_event_notifier /cgroup/A/memory.oom_control dummy
	(About cgroup_event_notifier, see Documentation/cgroup/)

Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Daisuke Nishimura 
Cc: Balbir Singh 
Cc: Daisuke Nishimura 
Cc: David Rientjes 
Cc: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation/: it's -> its where appropriate

2010-04-23T00:09:52+00:00

Fix obvious cases of "it's" being used when "its" was meant.

Signed-off-by: Francis Galiegue 
Acked-by: Randy Dunlap 
Signed-off-by: Jiri Kosina

memcg: fix typo in memcg documentation

2010-03-19T09:59:45+00:00

Updated memory.txt to be more consistent: s/swapiness/swappiness/

Signed-off-by: Greg Thelen 
Acked-by: Balbir Singh 
Signed-off-by: Jiri Kosina

memcg: handle panic_on_oom=always case

2010-03-12T23:52:37+00:00

Presently, if panic_on_oom=2, the whole system panics even if the oom
happend in some special situation (as cpuset, mempolicy....).  Then,
panic_on_oom=2 means painc_on_oom_always.

Now, memcg doesn't check panic_on_oom flag. This patch adds a check.

BTW, how it's useful ?

kdump+panic_on_oom=2 is the last tool to investigate what happens in
oom-ed system.  When a task is killed, the sysytem recovers and there will
be few hint to know what happnes.  In mission critical system, oom should
never happen.  Then, panic_on_oom=2+kdump is useful to avoid next OOM by
knowing precise information via snapshot.

TODO:
 - For memcg, it's for isolate system's memory usage, oom-notiifer and
   freeze_at_oom (or rest_at_oom) should be implemented. Then, management
   daemon can do similar jobs (as kdump) or taking snapshot per cgroup.

Signed-off-by: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Cc: David Rientjes 
Cc: Nick Piggin 
Reviewed-by: Daisuke Nishimura 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: implement memory thresholds

2010-03-12T23:52:37+00:00

It allows to register multiple memory and memsw thresholds and gets
notifications when it crosses.

To register a threshold application need:
- create an eventfd;
- open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
- write string like "  " to
  cgroup.event_control.

Application will be notified through eventfd when memory usage crosses
threshold in any direction.

It's applicable for root and non-root cgroup.

It uses stats to track memory usage, simmilar to soft limits. It checks
if we need to send event to userspace on every 100 page in/out. I guess
it's good compromise between performance and accuracy of thresholds.

[akpm@linux-foundation.org: coding-style fixes]
[nishimura@mxp.nes.nec.co.jp: fix documentation merge issue]
Signed-off-by: Kirill A. Shutemov 
Cc: Li Zefan 
Cc: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Cc: Pavel Emelyanov 
Cc: Dan Malek 
Cc: Vladislav Buzov 
Cc: Daisuke Nishimura 
Cc: Alexander Shishkin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: move charges of anonymous swap

2010-03-12T23:52:36+00:00

This patch is another core part of this move-charge-at-task-migration
feature.  It enables moving charges of anonymous swaps.

To move the charge of swap, we need to exchange swap_cgroup's record.

In current implementation, swap_cgroup's record is protected by:

  - page lock: if the entry is on swap cache.
  - swap_lock: if the entry is not on swap cache.

This works well in usual swap-in/out activity.

But this behavior make the feature of moving swap charge check many
conditions to exchange swap_cgroup's record safely.

So I changed modification of swap_cgroup's recored(swap_cgroup_record())
to use xchg, and define a new function to cmpxchg swap_cgroup's record.

This patch also enables moving charge of non pte_present but not uncharged
swap caches, which can be exist on swap-out path, by getting the target
pages via find_get_page() as do_mincore() does.

[kosaki.motohiro@jp.fujitsu.com: fix ia64 build]
[akpm@linux-foundation.org: fix typos]
Signed-off-by: Daisuke Nishimura 
Cc: Balbir Singh 
Acked-by: KAMEZAWA Hiroyuki 
Cc: Li Zefan 
Cc: Paul Menage 
Cc: Daisuke Nishimura 
Signed-off-by: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: add interface to move charge at task migration

2010-03-12T23:52:36+00:00

In current memcg, charges associated with a task aren't moved to the new
cgroup at task migration.  Some users feel this behavior to be strange.
These patches are for this feature, that is, for charging to the new
cgroup and, of course, uncharging from the old cgroup at task migration.

This patch adds "memory.move_charge_at_immigrate" file, which is a flag
file to determine whether charges should be moved to the new cgroup at
task migration or not and what type of charges should be moved.  This
patch also adds read and write handlers of the file.

This patch also adds no-op handlers for this feature.  These handlers will
be implemented in later patches.  And you cannot write any values other
than 0 to move_charge_at_immigrate yet.

Signed-off-by: Daisuke Nishimura 
Cc: Balbir Singh 
Acked-by: KAMEZAWA Hiroyuki 
Cc: Li Zefan 
Cc: Paul Menage 
Cc: Daisuke Nishimura 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds