Cgroups

Basic Information

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- Kernel feature that limits CPU, memory, Disk I/O and network usage of

  processes.

- More sophisticated than `ulimit`.

- Some resources that can be controlled via cgroups:

    a. cpu share

    b. cpu number to use

    c. memory

    d. and many more

Controllers

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memory	limits memory usage
cpuacct	monitors cpu usage

Tutorials

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Commands to check	# Check process cgroup membership ps -o cgroup <PID>
Creating cgroups manually (not persistent)	1. Install packages yum install libcgroup libcgroup-tools   2. Create group under memory controller mkdir /sys/fs/cgroup/memory/foo 3. Create this shell script #!/bin/bash while true; do   echo hello > /dev/null   sleep 1 done 4. Run script in background to emulate memory consuming process bash test.sh & 5. Apply memory limit under "foo" group echo 5 > /sys/fs/cgroup/memory/memory.limit_in_bytes 6. Get PID of script and include it under "foo" group echo (pgrep -f test.sh) > /sys/fs/cgroup/memory/foo/cgroup.procs 7. Notice that script was killed by OOM journalctl | tail
Creating cgroups using "libcgroup" (not persistent)	1. Install packages yum install libcgroup libcgroup-tools   2. Create group under memory controller cgcreate -g memory:foo 3. Create this shell script #!/bin/bash while true; do   echo hello > /dev/null   sleep 1 done 4. Run script in background to emulate memory consuming process cgexec -g memory:foo test.sh & 5. Apply memory limit under "foo" group echo 5 > /sys/fs/cgroup/memory/memory.limit_in_bytes 6. Notice that script was killed by OOM journalctl | tail
Enabling persistent configurations	1. Update /etc/cgconfig.conf   group foo {   cpu {     cpu.shares = 100;   }   memory {     memory.limit_in_bytes = 5;   } } 2. Enable service systemctl enable --now cgconfig 3. Run a program under cgroup control cgexec -g memory:foo test.sh &