linux.git/Documentation/cgroups/cgroups.txt, branch v2.6.30

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial

2009-04-03T22:24:35+00:00

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (28 commits)
  trivial: Update my email address
  trivial: NULL noise: drivers/mtd/tests/mtd_*test.c
  trivial: NULL noise: drivers/media/dvb/frontends/drx397xD_fw.h
  trivial: Fix misspelling of "Celsius".
  trivial: remove unused variable 'path' in alloc_file()
  trivial: fix a pdlfush -> pdflush typo in comment
  trivial: jbd header comment typo fix for JBD_PARANOID_IOFAIL
  trivial: wusb: Storage class should be before const qualifier
  trivial: drivers/char/bsr.c: Storage class should be before const qualifier
  trivial: h8300: Storage class should be before const qualifier
  trivial: fix where cgroup documentation is not correctly referred to
  trivial: Give the right path in Documentation example
  trivial: MTD: remove EOL from MODULE_DESCRIPTION
  trivial: Fix typo in bio_split()'s documentation
  trivial: PWM: fix of #endif comment
  trivial: fix typos/grammar errors in Kconfig texts
  trivial: Fix misspelling of firmware
  trivial: cgroups: documentation typo and spelling corrections
  trivial: Update contact info for Jochen Hein
  trivial: fix typo "resgister" -> "register"
  ...

cgroups: more documentation for remount and release_agent

2009-04-03T02:04:54+00:00

This won't remove cpuacct from the mounted hierachy:
 # mount -t cgroup -o cpu,cpuacct xxx /mnt
 # mount -o remount,cpu /mnt

Because for this usage mount(8) will append the new options to the original
options.

And this will get you right:
 # mount [-t cgroup] -o remount,cpu xxx /mnt

Also document how to specify or change release_agent.

Signed-off-by: Li Zefan 
Reviewd-by: KAMEZAWA Hiroyuki 
Cc: Paul Menage 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cgroup: fix frequent -EBUSY at rmdir

2009-04-03T02:04:54+00:00

In following situation, with memory subsystem,

	/groupA use_hierarchy==1
		/01 some tasks
		/02 some tasks
		/03 some tasks
		/04 empty

When tasks under 01/02/03 hit limit on /groupA, hierarchical reclaim
is triggered and the kernel walks tree under groupA. In this case,
rmdir /groupA/04 fails with -EBUSY frequently because of temporal
refcnt from the kernel.

In general. cgroup can be rmdir'd if there are no children groups and
no tasks. Frequent fails of rmdir() is not useful to users.
(And the reason for -EBUSY is unknown to users.....in most cases)

This patch tries to modify above behavior, by
	- retries if css_refcnt is got by someone.
	- add "return value" to pre_destroy() and allows subsystem to
	  say "we're really busy!"

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

trivial: cgroups: documentation typo and spelling corrections

2009-03-30T13:21:58+00:00

Minor typo and spelling corrections fixed whilst reading
to learn about cgroups capabilities.

Signed-off-by: Chris Samuel 
Acked-by: Paul Menage 
Signed-off-by: Jiri Kosina

cgroups: update documentation about css_set hash table

2009-02-18T23:37:53+00:00

The css_set hash table was introduced in 2.6.26, so update the
documentation accordingly.

Signed-off-by: Li Zefan 
Acked-by: Paul Menage 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cgroups: consolidate cgroup documents

2009-01-16T00:39:37+00:00

Move Documentation/cpusets.txt and Documentation/controllers/* to
Documentation/cgroups/

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

cgroups: add a per-subsystem hierarchy_mutex

2009-01-08T16:31:10+00:00

These patches introduce new locking/refcount support for cgroups to
reduce the need for subsystems to call cgroup_lock(). This will
ultimately allow the atomicity of cgroup_rmdir() (which was removed
recently) to be restored.

These three patches give:

1/3 - introduce a per-subsystem hierarchy_mutex which a subsystem can
     use to prevent changes to its own cgroup tree

2/3 - use hierarchy_mutex in place of calling cgroup_lock() in the
     memory controller

3/3 - introduce a css_tryget() function similar to the one recently
      proposed by Kamezawa, but avoiding spurious refcount failures in
      the event of a race between a css_tryget() and an unsuccessful
      cgroup_rmdir()

Future patches will likely involve:

- using hierarchy mutex in place of cgroup_lock() in more subsystems
 where appropriate

- restoring the atomicity of cgroup_rmdir() with respect to cgroup_create()

This patch:

Add a hierarchy_mutex to the cgroup_subsys object that protects changes to
the hierarchy observed by that subsystem.  It is taken by the cgroup
subsystem (in addition to cgroup_mutex) for the following operations:

- linking a cgroup into that subsystem's cgroup tree
- unlinking a cgroup from that subsystem's cgroup tree
- moving the subsystem to/from a hierarchy (including across the
  bind() callback)

Thus if the subsystem holds its own hierarchy_mutex, it can safely
traverse its own hierarchy.

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

cgroups: documentation updates

2009-01-08T16:31:01+00:00

- remove 'releasable' since it has been moved to the debug subsys.
- update lock requirements of subsys callbacks.

Signed-off-by: Li Zefan 
Cc: Paul Menage 
Cc: KAMEZAWA Hiroyuki 
Cc: Balbir Singh 
Cc: Pavel Emelyanov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

container freezer: document the cgroup freezer subsystem.

2008-10-20T15:52:34+00:00

Describe why we need the freezer subsystem and how to use it in a
documentation file.  Since the cgroups.txt file is focused on the
subsystem-agnostic portions of cgroups make a directory and move the old
cgroups.txt file at the same time.

Signed-off-by: Matt Helsley 
Cc: Paul Menage 
Cc: containers@lists.linux-foundation.org
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds