cgroups: Resource Limiting and Isolation in the Linux Kernel

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Control groups (cgroups) are a Linux kernel feature that limits, accounts for, and isolates the resource usage—such as CPU, memory, and disk I/O—of process collections.

Key points

  1. Initiated by Google engineers in 2006 as 'process containers', renamed to 'control groups' in 2007, and merged into Linux kernel mainline 2.6.24 in January 2008.
  2. Core features include resource limiting (memory, CPU quota, I/O bandwidth), prioritization, accounting, and process control (freezing and restarting).
  3. cgroup v2, introduced in Linux 4.5 (2016), enforces a single unified hierarchy and manages resources at process granularity rather than thread level.
  4. Interfacing occurs via a pseudo-filesystem (typically /sys/fs/cgroup), user-space tools (such as libcgroup), or higher-level tools like Docker, LXC, and systemd.
  5. Often used alongside Linux namespaces (e.g., PID, network, mount) to achieve process and resource isolation.

Why it matters

Alongside namespaces, cgroups serve as the foundational infrastructure for containerization technologies and system-level resource governance across modern Linux environments.

Analysis

The redesign from cgroup v1 to v2 addressed significant interface and architectural issues, eliminating multiple disparate controller hierarchies and thread discrimination. While v1 and v2 share the same codebase and can technically coexist, modern systems predominantly allocate all active controllers to the v2 hierarchy, tightly managed by init systems like systemd.

Mentioned links

Summary generated by AI (Gemini 3.8 Flash, 27 September 2026). It may contain errors – the original source is authoritative.

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