cgroup: make cgroup->nr_populated count the number of populated css_sets
Currently, cgroup->nr_populated counts whether the cgroup has any
css_sets linked to it and the number of children which has non-zero
->nr_populated. This works because a css_set's refcnt converges with
the number of tasks linked to it and thus there's no css_set linked to
a cgroup if it doesn't have any live tasks.
To help tracking resource usage of zombie tasks, putting the ref of
css_set will be separated from disassociating the task from the
css_set which means that a cgroup may have css_sets linked to it even
when it doesn't have any live tasks.
This patch updates cgroup->nr_populated so that for the cgroup itself
it counts the number of css_sets which have tasks associated with them
so that empty css_sets don't skew the populated test.
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index df589a0..1744450 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -232,10 +232,10 @@
int id;
/*
- * If this cgroup contains any tasks, it contributes one to
- * populated_cnt. All children with non-zero popuplated_cnt of
- * their own contribute one. The count is zero iff there's no task
- * in this cgroup or its subtree.
+ * Each non-empty css_set associated with this cgroup contributes
+ * one to populated_cnt. All children with non-zero popuplated_cnt
+ * of their own contribute one. The count is zero iff there's no
+ * task in this cgroup or its subtree.
*/
int populated_cnt;