Control Groups (ggroups)

• cgroup is a filesystem mounted into /sys/fs/cgroup
• All processes running on a linux machine is associated with a least one cgroup
• Group processes together and limit memory and cpu
• cgroups are arranged hierarchically
• a cgroup will inherit the configs of a parent cgroup

# List manually the tree of cgroups
ls /sys/fs/cgroup

# List via systemd
systemctl status

# Get the cgroup of a specific process
cat /proc/<pid>/cgroup

Cgroup example

# /etc/systemd/system/foo.slice
[Slice]
CPUQuota=30% # processes can take up to 30% of the CPU/thread
AllowedCPUs=0-5 # processes can use cpus 0 to 5 only
MemoryHigh=6G

# Run a shell attached to a cgroup
systemd-run --slice=foo.slice --uid=foo --shell