k3s/vendor/github.com/containerd/cgroups/README.md

cgroups

Go package for creating, managing, inspecting, and destroying cgroups. The resources format for settings on the cgroup uses the OCI runtime-spec found here.

Examples

Create a new cgroup

This creates a new cgroup using a static path for all subsystems under /test.

• /sys/fs/cgroup/cpu/test
• /sys/fs/cgroup/memory/test
• etc....

It uses a single hierarchy and specifies cpu shares as a resource constraint and uses the v1 implementation of cgroups.

shares := uint64(100)
control, err := cgroups.New(cgroups.V1, cgroups.StaticPath("/test"), &specs.LinuxResources{
    CPU: &specs.CPU{
        Shares: &shares,
    },
})
defer control.Delete()

Create with systemd slice support

control, err := cgroups.New(cgroups.Systemd, cgroups.Slice("system.slice", "runc-test"), &specs.LinuxResources{
    CPU: &specs.CPU{
        Shares: &shares,
    },
})

Load an existing cgroup

control, err = cgroups.Load(cgroups.V1, cgroups.StaticPath("/test"))

Add a process to the cgroup

if err := control.Add(cgroups.Process{Pid:1234}); err != nil {
}

Update the cgroup

To update the resources applied in the cgroup

shares = uint64(200)
if err := control.Update(&specs.LinuxResources{
    CPU: &specs.LinuxCPU{
        Shares: &shares,
    },
}); err != nil {
}

Freeze and Thaw the cgroup

if err := control.Freeze(); err != nil {
}
if err := control.Thaw(); err != nil {
}

List all processes in the cgroup or recursively

processes, err := control.Processes(cgroups.Devices, recursive)

Get Stats on the cgroup

stats, err := control.Stat()

By adding cgroups.IgnoreNotExist all non-existent files will be ignored, e.g. swap memory stats without swap enabled

stats, err := control.Stat(cgroups.IgnoreNotExist)

Move process across cgroups

This allows you to take processes from one cgroup and move them to another.

err := control.MoveTo(destination)

Create subcgroup

subCgroup, err := control.New("child", resources)

Registering for memory events

This allows you to get notified by an eventfd for v1 memory cgroups events.

event := cgroups.MemoryThresholdEvent(50 * 1024 * 1024, false)
efd, err := control.RegisterMemoryEvent(event)

event := cgroups.MemoryPressureEvent(cgroups.MediumPressure, cgroups.DefaultMode)
efd, err := control.RegisterMemoryEvent(event)

efd, err := control.OOMEventFD()
// or by using RegisterMemoryEvent
event := cgroups.OOMEvent()
efd, err := control.RegisterMemoryEvent(event)

Attention

All static path should not include /sys/fs/cgroup/ prefix, it should start with your own cgroups name

Project details

Cgroups is a containerd sub-project, licensed under the Apache 2.0 license. As a containerd sub-project, you will find the:

• Project governance,
• Maintainers,
• and Contributing guidelines

information in our containerd/project repository.