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 (v1)

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:=cgroup1.New(cgroup1.StaticPath("/test"), &specs.LinuxResources{
CPU: &specs.LinuxCPU{
Shares: &shares,
},
})
defercontrol.Delete()

Create with systemd slice support

control, err:=cgroup1.New(cgroup1.Systemd, cgroup1.Slice("system.slice", "runc-test"), &specs.LinuxResources{
CPU: &specs.CPU{
Shares: &shares,
},
})

Load an existing cgroup

control, err=cgroup1.Load(cgroup1.Default, cgroups.StaticPath("/test"))

Add a process to the cgroup

iferr:=control.Add(cgroup1.Process{Pid:1234}); err!=nil {
}

Update the cgroup

To update the resources applied in the cgroup

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

Freeze and Thaw the cgroup

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

List all processes in the cgroup or recursively

processes, err:=control.Processes(cgroup1.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(cgroup1.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:=cgroup1.MemoryThresholdEvent(50*1024*1024, false)
efd, err:=control.RegisterMemoryEvent(event)

event:=cgroup1.MemoryPressureEvent(cgroup1.MediumPressure, cgroup1.DefaultMode)
efd, err:=control.RegisterMemoryEvent(event)

efd, err:=control.OOMEventFD()
// or by using RegisterMemoryEventevent:=cgroup1.OOMEvent()
efd, err:=control.RegisterMemoryEvent(event)

Examples (v2/unified)

Check that the current system is running cgroups v2

varcgroupV2boolifcgroups.Mode() ==cgroups.Unified {
cgroupV2=true
}

Create a new cgroup

This creates a new systemd v2 cgroup slice. Systemd slices consider "-" a special character, so the resulting slice would be located here on disk:

• /sys/fs/cgroup/my.slice/my-cgroup.slice/my-cgroup-abc.slice

import (
"github.com/containerd/cgroups/v3/cgroup2"
specs "github.com/opencontainers/runtime-spec/specs-go"
)
res:= cgroup2.Resources{}
// dummy PID of -1 is used for creating a "general slice" to be used as a parent cgroup.// see https://github.com/containerd/cgroups/blob/1df78138f1e1e6ee593db155c6b369466f577651/v2/manager.go#L732-L735m, err:=cgroup2.NewSystemd("/", "my-cgroup-abc.slice", -1, &res)
iferr!=nil {
returnerr
}

Load an existing cgroup

m, err:=cgroup2.LoadSystemd("/", "my-cgroup-abc.slice")
iferr!=nil {
returnerr
}

Delete a cgroup

m, err:=cgroup2.LoadSystemd("/", "my-cgroup-abc.slice")
iferr!=nil {
returnerr
}
err=m.DeleteSystemd()
iferr!=nil {
returnerr
}

Kill all processes in a cgroup

m, err:=cgroup2.LoadSystemd("/", "my-cgroup-abc.slice")
iferr!=nil {
returnerr
}
err=m.Kill()
iferr!=nil {
returnerr
}

Get and set cgroup type

m, err:=cgroup2.LoadSystemd("/", "my-cgroup-abc.slice")
iferr!=nil {
returnerr
}
// https://www.kernel.org/doc/html/v5.0/admin-guide/cgroup-v2.html#threadscgType, err:=m.GetType()
iferr!=nil {
returnerr
}
fmt.Println(cgType)
err=m.SetType(cgroup2.Threaded)
iferr!=nil {
returnerr
}

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.