Understanding cgroups: Why Systemd Forked Processes are Different

In systemd, a forked process, created by a parent process using the 'fork' system call, is an almost identical copy of its parent. However, each forked process in systemd gets placed in its own cgroup, unlike its parent. But what are cgroups and why are they important?

Cgroups, short for control groups, are a powerful Linux kernel feature. They allow for resource allocation and limit setting for groups of processes. By placing each forked process in its own cgroup, systemd gains granular control over the resource usage of every process.

This separation offers several advantages:

• Effective Resource Management: Systemd can apply specific resource limits like CPU time or memory usage to individual processes, preventing any single process from monopolizing system resources.* Enhanced Process Supervision: Systemd can track and manage the lifecycle of each forked process independently, enabling actions like restarting a failed process without impacting other processes within the same service.* Improved Service Control: cgroups allow systemd to manage and control services composed of multiple processes more efficiently.

In essence, systemd leverages cgroups to treat each forked process as a distinct entity, facilitating better resource utilization, process monitoring, and overall system stability.