admin-guide/cgroup-v1/pids.rst

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9 new tasks from being fork()'d or clone()'d after a certain limit is reached.
11 Since it is trivial to hit the task limit without hitting any kmemcg limits in
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21 number of processes currently in the cgroup is given by pids.current.
24 to have pids.current > pids.max. This can be done by either setting the limit to
25 be smaller than pids.current, or attaching enough processes to the cgroup such
26 that pids.current > pids.max. However, it is not possible to violate a cgroup
27 policy through fork() or clone(). fork() and clone() will return -EAGAIN if the
30 To set a cgroup to have no limit, set pids.max to "max". This is the default for
32 limit in the hierarchy is followed).
34 pids.current tracks all child cgroup hierarchies, so parent/pids.current is a
35 superset of parent/child/pids.current.
39   - max: Number of times fork failed because limit was hit.
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46 	# mkdir -p /sys/fs/cgroup/pids
47 	# mount -t cgroup -o pids none /sys/fs/cgroup/pids
51 	# mkdir -p /sys/fs/cgroup/pids/parent/child
54 	# cat /sys/fs/cgroup/pids/parent/pids.current
58 It should be noted that attempts to overcome the set limit (2 in this case) will
61 	# cat /sys/fs/cgroup/pids/parent/pids.current
67 Even if we migrate to a child cgroup (which doesn't have a set limit), we will
68 not be able to overcome the most stringent limit in the hierarchy (in this case,
72 	# cat /sys/fs/cgroup/pids/parent/pids.current
74 	# cat /sys/fs/cgroup/pids/parent/child/pids.current
82 We can set a limit that is smaller than pids.current, which will stop any new
84 pids.current)::