What are groups used for?

Control Groups (cgroups) are used to manage and isolate resources such as CPU, memory, input/output, and network resources for groups of processes. They enable efficient distribution and limiting of resource consumption, which is important for containerization, OS-level virtualization, and load management in systems.

Key features:

• Resource Limiting: Set limits on CPU, memory, etc.

  # Limit memory usage to 100MB for the "mygroup" group
  echo 100M > /sys/fs/cgroup/memory/mygroup/memory.limit_in_bytes
  

• Prioritization: Assign different priorities for resource access.

  # Allocate more CPU time to the "high_prio" group
  echo 1024 > /sys/fs/cgroup/cpu/high_prio/cpu.shares
  # Less for the "low_prio" group
  echo 512 > /sys/fs/cgroup/cpu/low_prio/cpu.shares
  

• Usage Monitoring: Monitor how much resources a process group consumes.

  # Read memory usage statistics for the "mygroup" group
  cat /sys/fs/cgroup/memory/mygroup/memory.stat
  

• Control: Forcefully terminate processes when limits are exceeded.

Applying control groups is fundamental for technologies like Docker, Kubernetes, and LXC, providing the necessary level of isolation and resource management for containers.