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Description
While working on docker/compose#2114, I noticed that docker handles cgroups hierarchies via cgroup-parent flag a little differently.
For ex:
First, I launched a parent docker container using:
docker run busybox ping www.docker.com
For this container daemon creates a cgroup here:
# cat /proc/10968/cgroup
...
8:memory:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope
6:cpuset:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope
5:net_cls,net_prio:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope
2:cpu,cpuacct:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope
...
Next, I launch another container using cgroup-parent flag:
docker run --cgroup-parent docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope busybox ping www.paypal.com
For this container, docker creates a cgroup, but the hierarchy is broken:
# cat /proc/11105/cgroup
...
8:memory:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope-33917fb99f596633a1731a90f91b1d079528c6898e512e90b6eae89af462c52a.scope
6:cpuset:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope-33917fb99f596633a1731a90f91b1d079528c6898e512e90b6eae89af462c52a.scope
5:net_cls,net_prio:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope-33917fb99f596633a1731a90f91b1d079528c6898e512e90b6eae89af462c52a.scope
2:cpu,cpuacct:/system.slice/docker-773e468adb0e97459059804f5906fee50edfe37fb4babad5655508fa7a1f27e0.scope-33917fb99f596633a1731a90f91b1d079528c6898e512e90b6eae89af462c52a.scope
...
Is this the expected behavior ? I assumed that cgroup-parent flag should nest the child's cgroup under the parent.
Here's are some details of my system:
# docker version
Client:
Version: 1.8.2
API version: 1.20
Go version: go1.4.2
Git commit: 0a8c2e3
Built: Thu Sep 10 19:21:21 UTC 2015
OS/Arch: linux/amd64
Server:
Version: 1.8.2
API version: 1.20
Go version: go1.4.2
Git commit: 0a8c2e3
Built: Thu Sep 10 19:21:21 UTC 2015
OS/Arch: linux/amd64
# uname -a
Linux mohit-mate 3.19.0-15-generic #15-Ubuntu SMP Thu Apr 16 23:32:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
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