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Merge pull request #2359 from teawater/swap_doc

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Add doc for guest swap
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Tim Zhang 2021-09-14 15:54:10 +08:00 committed by GitHub
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1
docs/how-to/README.md
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@ -34,3 +34,4 @@
- [How to set sandbox Kata Containers configurations with pod annotations](how-to-set-sandbox-config-kata.md)
- [How to monitor Kata Containers in K8s](how-to-set-prometheus-in-k8s.md)
- [How to use hotplug memory on arm64 in Kata Containers](how-to-hotplug-memory-arm64.md)
- [How to setup swap devices in guest kernel](how-to-setup-swap-devices-in-guest-kernel.md)

19
docs/how-to/how-to-set-sandbox-config-kata.md
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@ -91,6 +91,13 @@ There are several kinds of Kata configurations and they are listed below.
| `io.katacontainers.config.hypervisor.virtio_fs_cache` | string | the cache mode for virtio-fs, valid values are `always`, `auto` and `none` |
| `io.katacontainers.config.hypervisor.virtio_fs_daemon` | string | virtio-fs `vhost-user` daemon path |
| `io.katacontainers.config.hypervisor.virtio_fs_extra_args` | string | extra options passed to `virtiofs` daemon |
| `io.katacontainers.config.hypervisor.enable_guest_swap` | `boolean` | enable swap in the guest |
## Container Options
| Key | Value Type | Comments |
|-------| ----- | ----- |
| `io.katacontainers.container.resource.swappiness"` | `uint64` | specify the `Resources.Memory.Swappiness` |
| `io.katacontainers.container.resource.swap_in_bytes"` | `uint64` | specify the `Resources.Memory.Swap` |
# CRI-O Configuration
@ -100,11 +107,12 @@ In case of CRI-O, all annotations specified in the pod spec are passed down to K
For containerd, annotations specified in the pod spec are passed down to Kata
starting with version `1.3.0` of containerd. Additionally, extra configuration is
needed for containerd, by providing a `pod_annotations` field in the containerd config
file. The `pod_annotations` field is a list of annotations that can be passed down to
Kata as OCI annotations. It supports golang match patterns. Since annotations supported
by Kata follow the pattern `io.katacontainers.*`, the following configuration would work
for passing annotations to Kata from containerd:
needed for containerd, by providing `pod_annotations` field and
`container_annotations` field in the containerd config
file. The `pod_annotations` field and `container_annotations` field are two lists of
annotations that can be passed down to Kata as OCI annotations. They support golang match
patterns. Since annotations supported by Kata follow the pattern `io.katacontainers.*`,
the following configuration would work for passing annotations to Kata from containerd:
```
$ cat /etc/containerd/config
@ -113,6 +121,7 @@ $ cat /etc/containerd/config
[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.kata]
runtime_type = "io.containerd.kata.v2"
pod_annotations = ["io.katacontainers.*"]
container_annotations = ["io.katacontainers.*"]
....
```

59
docs/how-to/how-to-setup-swap-devices-in-guest-kernel.md Normal file
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@ -0,0 +1,59 @@
# Setup swap device in guest kernel
## Introduction
Setup swap device in guest kernel can help to increase memory capacity, handle some memory issues and increase file access speed sometimes.
Kata Containers can insert a raw file to the guest as the swap device.
## Requisites
The swap config of the containers should be set by [annotations](how-to-set-sandbox-config-kata.md#container-options). So [extra configuration is needed for containerd](how-to-set-sandbox-config-kata.md#containerd-configuration).
Kata Containers just supports setup swap device in guest kernel with QEMU.
Install and setup Kata Containers as shown [here](../install/README.md).
Enable setup swap device in guest kernel as follows:
```
$ sudo sed -i -e 's/^#enable_guest_swap.*$/enable_guest_swap = true/g' /etc/kata-containers/configuration.toml
```
## Run a Kata Container utilizing swap device
Use following command to start a Kata Container with swappiness 60 and 1GB swap device (swap_in_bytes - memory_limit_in_bytes).
```
$ pod_yaml=pod.yaml
$ container_yaml=container.yaml
$ image="quay.io/prometheus/busybox:latest"
$ cat << EOF > "${pod_yaml}"
metadata:
name: busybox-sandbox1
EOF
$ cat << EOF > "${container_yaml}"
metadata:
name: busybox-test-swap
annotations:
io.katacontainers.container.resource.swappiness: "60"
io.katacontainers.container.resource.swap_in_bytes: "2147483648"
linux:
resources:
memory_limit_in_bytes: 1073741824
image:
image: "$image"
command:
- top
EOF
$ sudo crictl pull $image
$ podid=$(sudo crictl runp $pod_yaml)
$ cid=$(sudo crictl create $podid $container_yaml $pod_yaml)
$ sudo crictl start $cid
```
Kata Container setups swap device for this container only when `io.katacontainers.container.resource.swappiness` is set.
The following table shows the swap size how to decide if `io.katacontainers.container.resource.swappiness` is set.
|`io.katacontainers.container.resource.swap_in_bytes`|`memory_limit_in_bytes`|swap size|
|---|---|---|
|set|set| `io.katacontainers.container.resource.swap_in_bytes` - `memory_limit_in_bytes`|
|not set|set| `memory_limit_in_bytes`|
|not set|not set| `io.katacontainers.config.hypervisor.default_memory`|
|set|not set|cgroup doesn't support this usage|