kata-containers/docs/how-to/how-to-use-virtio-mem-with-kata.md
James O. D. Hunt 4f0726bc49 docs: Remove table of contents
Removed all TOCs now that GitHub auto-generates them.

Also updated the documentation requirements doc removing the requirement
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Fixes: #2022.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>
2021-07-30 10:58:22 +01:00

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# Kata Containers with `virtio-mem`
## Introduction
The basic idea of `virtio-mem` is to provide a flexible, cross-architecture memory hot plug and hot unplug solution that avoids many limitations imposed by existing technologies, architectures, and interfaces.
More details can be found in https://lkml.org/lkml/2019/12/12/681.
Kata Containers with `virtio-mem` supports memory resize.
## Requisites
Kata Containers just supports `virtio-mem` with QEMU.
Install and setup Kata Containers as shown [here](../install/README.md).
### With x86_64
The `virtio-mem` config of the x86_64 Kata Linux kernel is open.
Enable `virtio-mem` as follows:
```
$ sudo sed -i -e 's/^#enable_virtio_mem.*$/enable_virtio_mem = true/g' /etc/kata-containers/configuration.toml
```
### With other architectures
The `virtio-mem` config of the others Kata Linux kernel is not open.
You can open `virtio-mem` config as follows:
```
CONFIG_VIRTIO_MEM=y
```
Then you can build and install the guest kernel image as shown [here](../../tools/packaging/kernel/README.md#build-kata-containers-kernel).
## Run a Kata Container utilizing `virtio-mem`
Use following command to enable memory overcommitment of a Linux kernel. Because QEMU `virtio-mem` device need to allocate a lot of memory.
```
$ echo 1 | sudo tee /proc/sys/vm/overcommit_memory
```
Use following command to start a Kata Container.
```
$ 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 > "${container_yaml}"
metadata:
name: busybox-killed-vmm
image:
image: "$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
```
Use the following command to set the container memory limit to 2g and the memory size of the VM to its default_memory + 2g.
```
$ sudo crictl update --memory $((2*1024*1024*1024)) $cid
```
Use the following command to set the container memory limit to 1g and the memory size of the VM to its default_memory + 1g.
```
$ sudo crictl update --memory $((1*1024*1024*1024)) $cid
```