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cgroup: make cgroup->nr_populated count the number of populated css_sets

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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>
This commit is contained in:
Tejun Heo 2015-10-15 16:41:49 -04:00
parent b309e5b743
commit 0de0942db2
2 changed files with 56 additions and 17 deletions
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8
include/linux/cgroup-defs.h
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@ -232,10 +232,10 @@ struct cgroup {
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;