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17af28acad
Add how-to-use-memory-agent.md (How to use mem-agent to decrease the memory usage of Kata container) to docs to show how to use mem-agent. Fixes: #11013 Signed-off-by: Hui Zhu <teawater@gmail.com>
64 lines
2.5 KiB
Markdown
64 lines
2.5 KiB
Markdown
# Setup swap device in guest kernel
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## Introduction
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This document describes how to setup swap device with runtime-golang. See [How to use mem-agent to decrease the memory usage of Kata container](how-to-use-memory-agent.md#setup-guest-swap) to get how to setup and use guest swap with runtime-rs.
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Setup swap device in guest kernel can help to increase memory capacity, handle some memory issues and increase file access speed sometimes.
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Kata Containers can insert a raw file to the guest as the swap device.
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## Requisites
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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).
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Kata Containers just supports setup swap device in guest kernel with QEMU.
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Install and setup Kata Containers as shown [here](../install/README.md).
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Enable setup swap device in guest kernel as follows:
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```
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$ sudo sed -i -e 's/^#enable_guest_swap.*$/enable_guest_swap = true/g' /etc/kata-containers/configuration.toml
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```
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## Run a Kata Containers utilizing swap device
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Use following command to start a Kata Containers with swappiness 60 and 1GB swap device (swap_in_bytes - memory_limit_in_bytes).
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```
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$ pod_yaml=pod.yaml
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$ container_yaml=container.yaml
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$ image="quay.io/prometheus/busybox:latest"
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$ cat << EOF > "${pod_yaml}"
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metadata:
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name: busybox-sandbox1
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uid: $(uuidgen)
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namespace: default
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EOF
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$ cat << EOF > "${container_yaml}"
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metadata:
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name: busybox-test-swap
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annotations:
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io.katacontainers.container.resource.swappiness: "60"
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io.katacontainers.container.resource.swap_in_bytes: "2147483648"
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linux:
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resources:
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memory_limit_in_bytes: 1073741824
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image:
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image: "$image"
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command:
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- top
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EOF
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$ sudo crictl pull $image
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$ podid=$(sudo crictl runp --runtime kata $pod_yaml)
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$ cid=$(sudo crictl create $podid $container_yaml $pod_yaml)
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$ sudo crictl start $cid
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```
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Kata Containers setups swap device for this container only when `io.katacontainers.container.resource.swappiness` is set.
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The following table shows the swap size how to decide if `io.katacontainers.container.resource.swappiness` is set.
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|`io.katacontainers.container.resource.swap_in_bytes`|`memory_limit_in_bytes`|swap size|
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|---|---|---|
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|set|set| `io.katacontainers.container.resource.swap_in_bytes` - `memory_limit_in_bytes`|
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|not set|set| `memory_limit_in_bytes`|
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|not set|not set| `io.katacontainers.config.hypervisor.default_memory`|
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|set|not set|cgroup doesn't support this usage|
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