memcg: track all children over limit in the root

Children in soft limit excess are currently tracked up the hierarchy in
memcg->children_in_excess.  Nevertheless there still might exist tons of
groups that are not in hierarchy relation to the root cgroup (e.g.  all
first level groups if root_mem_cgroup->use_hierarchy == false).

As the whole tree walk has to be done when the iteration starts at
root_mem_cgroup the iterator should be able to skip the walk if there is
no child above the limit without iterating them.  This can be done
easily if the root tracks all children rather than only hierarchical
children.  This is done by this patch which updates root_mem_cgroup
children_in_excess if root_mem_cgroup->use_hierarchy == false so the
root knows about all children in excess.

Please note that this is not an issue for inner memcgs which have
use_hierarchy == false because then only the single group is visited so
no special optimization is necessary.

Signed-off-by: Michal Hocko <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Glauber Costa <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Ying Han <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions