cgroup
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/resource_management_guide/ch01
http://man7.org/linux/man-pages/man7/cgroups.7.html
https://www.ibm.com/developerworks/cn/linux/1506_cgroup/index.html
docker&cgroups
http://www.infoq.com/cn/articles/docker-kernel-knowledge-cgroups-resource-isolation
https://yq.aliyun.com/articles/64965