System information

Kernel Control Groups 121
Kernel Control Groups
10
Kernel Control Groups (abbreviated known as “cgroups”) are a kernel feature that al-
lows aggregating or partitioning tasks (processes) and all their children into hierarchi-
cal organized groups. These hierarchical groups can be configured to show a special-
ized behavior that helps with tuning the system to make best use of available hardware
and network resources.
10.1 Technical Overview and
Definitions
The following terms are used in this chapter:
• “cgroup” is another name for Control Groups.
• In a cgroup there is a set of tasks (processes) associated with a set of subsystems
that act as parameters constituting an environment for the tasks.
• Subsystems provide the parameters that can be assigned and define CPU sets,
freezer, or—more general—“resource controllers” for memory, disk I/O, network
traffic, etc.
• cgroups are organized in a tree-structured hierarchy. There can be more than one
hierarchy in the system. You use a different or alternate hierarchy to cope with spe-
cific situations.