cgroup v1
also: control groups v1, cgroupv1
The original implementation of Linux control groups, allowing administrators to limit and monitor resource usage (CPU, memory, I/O) for groups of processes. Largely superseded by cgroup v2 but still widely supported.
cgroup v1 (control groups version 1) is a kernel mechanism that organizes processes into hierarchical groups and applies resource constraints to each group. Each resource type (CPU, memory, block I/O, network) has its own separate hierarchy, giving fine-grained control but added complexity.
For example, you might create a cgroup to limit a web server process and its children to 2 GB of memory and 50% CPU time: echo 2000000000 > /sys/fs/cgroup/memory/myapp/memory.limit_in_bytes. The process is added by writing its PID to cgroups.procs.
cgroup v1 remains in production use and is often preferred for compatibility with older tools and systems, though most new deployments favor cgroup v2, which unifies resource types into a single hierarchy and provides cleaner semantics.