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57 lines
1.7 KiB
Plaintext
57 lines
1.7 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * virt/virtual_machines/advanced_vm_management/virt-managing-guest-memory.adoc
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[id="virt-configuring-guest-memory-overcommitment_{context}"]
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= Configuring guest memory overcommitment
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If your virtual workload requires more memory than available, you can
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use memory overcommitment to allocate all or most of the host’s memory
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to your virtual machine instances. Enabling memory overcommitment means
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you can maximize resources that are normally reserved for the host.
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For example, if the host has 32 GB RAM, you can use memory
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overcommitment to fit 8 virtual machines with 4 GB RAM each. This allocation works under the
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assumption that the virtual machines will not use all of their memory at the same
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time.
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.Procedure
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. To explicitly tell the virtual machine instance that it has more memory available than
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was requested from the cluster, edit the virtual machine configuration file and
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set `spec.domain.memory.guest` to a higher value than
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`spec.domain.resources.requests.memory`. This process is called memory
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overcommitment.
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+
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In this example, `1024M` is requested from the cluster, but the virtual machine instance is
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told that it has `2048M` available. As long as there is enough free memory
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available on the node, the virtual machine instance will consume up to 2048M.
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+
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[source,yaml]
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----
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kind: VirtualMachine
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spec:
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template:
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domain:
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resources:
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requests:
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memory: 1024M
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memory:
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guest: 2048M
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----
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+
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[NOTE]
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====
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The same eviction rules as those for pods apply to the virtual machine instance if
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the node is under memory pressure.
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====
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. Create the virtual machine:
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+
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[source,terminal]
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----
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$ oc create -f <file name>.yaml
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----
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