Linux cgroups

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Revision as of 19:46, 6 February 2018 by Ovidiu (talk | contribs) (→‎Overview)
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Overview

cgroups is a Linux kernel feature that allows allocation of resources (CPU, system memory, network bandwidth, or a combination of these) among user-defined groups of processes running on the system. cgroups not only track groups of processes, but they also expose metrics about CPU, memory and block I/O usage.

cgroups are exposed through a pseudo-filesystem available at /sys/fs/cgroup (older systems expose it at /cgroup). The sub-directories of the cgroup pseudo-filesystem root correspond to different cgroups hierarchies: devices, freezer, blkio.

cgroups are organized hierarchically, child cgroups inheriting certain attributes from their parent group. Many different hierarchies of cgroups can exist simultaneously on a system. Each hierarchy is attached to one or more subsystem, where a subsystem represents a single resource like CPU time or memory.

cgroups can be configured via the cgconfig service.

cgroups Subsystems

  • blkio - sets limits on input/output access from and to block devices.
  • cpu - uses the scheduler to provide cgroup tasks access to the CPU.
  • cpuacct - generates automatic reports on CPU resources.
  • cpuset - assigns individual CPUs and memory nodes to tasks in a cgroup.
  • devices.
  • freezer.
  • memory.
  • net_cls - tags network packets with a tag identifier (classid) that allow the Linux traffic controller (tc) to identify packets.
  • net_prio.
  • ns - the namespace subsystem.
  • perf_event.

Operations

The recommended location for cgroup hierarchies:

/sys/fs/cgroup