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When starting a VM on KVM, ACS sets VM's CPU topology through a calculation of CPU sockets and CPU cores per socket on VM's XML. Along the calculation, for instance, it assumes that a VM that use 12 vCPUs automatically works with 2 sockets and 6 cores, or a VM that use 16 vCPUs automatically works 4 sockets and 4 cores:
This behavior is arbitrary and operators cannot choose to use it or not.
By default (fedora - Setting KVM processor affinities), if we not determine the CPU topology, the hypervisor will alloc the VM on any available CPU; Therefore, this PR intends to externalize a property (enable.manually.setting.cpu.topology.on.kvm.vm) on agent.properties to allow the operators to decide if they want to do the calculation or not. The default behavior still will be to do the calculation.
Types of changes
Breaking change (fix or feature that would cause existing functionality to change)
New feature (non-breaking change which adds functionality)
Bug fix (non-breaking change which fixes an issue)
Enhancement (improves an existing feature and functionality)
Cleanup (Code refactoring and cleanup, that may add test cases)
Feature/Enhancement Scale or Bug Severity
Feature/Enhancement Scale
Major
Minor
How Has This Been Tested?
It was tested on a local lab.
I created a host with 1 socket and 8 cores;
I created a VM with 8 vCPUs;
When the property doesn't exist in the file or when it is true, the topology is set:
<topology sockets='2' cores='4' threads='1'/>;
When the property is set to false, the topology is not set;
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Description
When starting a VM on KVM, ACS sets VM's CPU topology through a calculation of CPU sockets and CPU cores per socket on VM's XML. Along the calculation, for instance, it assumes that a VM that use 12 vCPUs automatically works with 2 sockets and 6 cores, or a VM that use 16 vCPUs automatically works 4 sockets and 4 cores:
cloudstack/plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtComputingResource.java
Lines 4504 to 4524 in d6a77a7
This behavior is arbitrary and operators cannot choose to use it or not.
By default (fedora - Setting KVM processor affinities), if we not determine the CPU topology, the hypervisor will alloc the VM on any available CPU; Therefore, this PR intends to externalize a property (
enable.manually.setting.cpu.topology.on.kvm.vm) onagent.propertiesto allow the operators to decide if they want to do the calculation or not. The default behavior still will be to do the calculation.Types of changes
Feature/Enhancement Scale or Bug Severity
Feature/Enhancement Scale
How Has This Been Tested?
It was tested on a local lab.
<topology sockets='2' cores='4' threads='1'/>;false, the topology is not set;