gotosocial/vendor/github.com/containerd/cgroups/README.md
Daniele Sluijters acc333c40b
[feature] Inherit resource limits from cgroups (#1336)
When GTS is running in a container runtime which has configured CPU or
memory limits or under an init system that uses cgroups to impose CPU
and memory limits the values the Go runtime sees for GOMAXPROCS and
GOMEMLIMIT are still based on the host resources, not the cgroup.

At least for the throttling middlewares which use GOMAXPROCS to
configure their queue size, this can result in GTS running with values
too big compared to the resources that will actuall be available to it.

This introduces 2 dependencies which can pick up resource contraints
from the current cgroup and tune the Go runtime accordingly. This should
result in the different queues being appropriately sized and in general
more predictable performance. These dependencies are a no-op on
non-Linux systems or if running in a cgroup that doesn't set a limit on
CPU or memory.

The automatic tuning of GOMEMLIMIT can be disabled by either explicitly
setting GOMEMLIMIT yourself or by setting AUTOMEMLIMIT=off. The
automatic tuning of GOMAXPROCS can similarly be counteracted by setting
GOMAXPROCS yourself.
2023-01-17 20:59:04 +00:00

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# cgroups
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[![Go Report Card](https://goreportcard.com/badge/github.com/containerd/cgroups)](https://goreportcard.com/report/github.com/containerd/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](https://github.com/opencontainers/runtime-spec).
## 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.
```go
shares := uint64(100)
control, err := cgroups.New(cgroups.V1, cgroups.StaticPath("/test"), &specs.LinuxResources{
CPU: &specs.LinuxCPU{
Shares: &shares,
},
})
defer control.Delete()
```
### Create with systemd slice support
```go
control, err := cgroups.New(cgroups.Systemd, cgroups.Slice("system.slice", "runc-test"), &specs.LinuxResources{
CPU: &specs.CPU{
Shares: &shares,
},
})
```
### Load an existing cgroup
```go
control, err = cgroups.Load(cgroups.V1, cgroups.StaticPath("/test"))
```
### Add a process to the cgroup
```go
if err := control.Add(cgroups.Process{Pid:1234}); err != nil {
}
```
### Update the cgroup
To update the resources applied in the cgroup
```go
shares = uint64(200)
if err := control.Update(&specs.LinuxResources{
CPU: &specs.LinuxCPU{
Shares: &shares,
},
}); err != nil {
}
```
### Freeze and Thaw the cgroup
```go
if err := control.Freeze(); err != nil {
}
if err := control.Thaw(); err != nil {
}
```
### List all processes in the cgroup or recursively
```go
processes, err := control.Processes(cgroups.Devices, recursive)
```
### Get Stats on the cgroup
```go
stats, err := control.Stat()
```
By adding `cgroups.IgnoreNotExist` all non-existent files will be ignored, e.g. swap memory stats without swap enabled
```go
stats, err := control.Stat(cgroups.IgnoreNotExist)
```
### Move process across cgroups
This allows you to take processes from one cgroup and move them to another.
```go
err := control.MoveTo(destination)
```
### Create subcgroup
```go
subCgroup, err := control.New("child", resources)
```
### Registering for memory events
This allows you to get notified by an eventfd for v1 memory cgroups events.
```go
event := cgroups.MemoryThresholdEvent(50 * 1024 * 1024, false)
efd, err := control.RegisterMemoryEvent(event)
```
```go
event := cgroups.MemoryPressureEvent(cgroups.MediumPressure, cgroups.DefaultMode)
efd, err := control.RegisterMemoryEvent(event)
```
```go
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](./LICENSE).
As a containerd sub-project, you will find the:
* [Project governance](https://github.com/containerd/project/blob/main/GOVERNANCE.md),
* [Maintainers](https://github.com/containerd/project/blob/main/MAINTAINERS),
* and [Contributing guidelines](https://github.com/containerd/project/blob/main/CONTRIBUTING.md)
information in our [`containerd/project`](https://github.com/containerd/project) repository.