path: root/Documentation
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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2012-05-29 15:07:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-29 16:22:27 -0700
commitcc926f78420705817b807dbec0c5d3643827eba3 (patch)
treefea47aea4b5963fbf06e77c593abeee3afb1958b /Documentation
parentmemcg: use res_counter_uncharge_until() in move_parent() (diff)
memcg: move charges to root cgroup if use_hierarchy=0
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 <kamezawa.hiroyu@jp.fujitsu.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ying Han <yinghan@google.com> Cc: Glauber Costa <glommer@parallels.com> Reviewed-by: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
1 files changed, 8 insertions, 5 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 6a066a270fc5..dd88540bb995 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -376,14 +376,15 @@ cgroup might have some charge associated with it, even though all
tasks have migrated away from it. (because we charge against pages, not
against tasks.)
-Such charges are freed or moved to their parent. At moving, both of RSS
-and CACHES are moved to parent.
-rmdir() may return -EBUSY if freeing/moving fails. See 5.1 also.
+We move the stats to root (if use_hierarchy==0) or parent (if
+use_hierarchy==1), and no change on the charge except uncharging
+from the child.
Charges recorded in swap information is not updated at removal of cgroup.
Recorded information is discarded and a cgroup which uses swap (swapcache)
will be charged as a new owner of it.
+About use_hierarchy, see Section 6.
5. Misc. interfaces.
@@ -396,13 +397,15 @@ will be charged as a new owner of it.
Almost all pages tracked by this memory cgroup will be unmapped and freed.
Some pages cannot be freed because they are locked or in-use. Such pages are
- moved to parent and this cgroup will be empty. This may return -EBUSY if
- VM is too busy to free/move all pages immediately.
+ moved to parent(if use_hierarchy==1) or root (if use_hierarchy==0) and this
+ cgroup will be empty.
Typical use case of this interface is that calling this before rmdir().
Because rmdir() moves all pages to parent, some out-of-use page caches can be
moved to the parent. If you want to avoid that, force_empty will be useful.
+ About use_hierarchy, see Section 6.
5.2 stat file
memory.stat file includes following statistics