Live resizing CPU and memory

Limitations

The functionality has the following limitations:

• Not compatible with OpenNebula’s NUMA configuration

• Not compatible with hugepages

Tested with OpenNebula 5.10; should work with 5.12. 6.0+ has native functionality.

Installation

1. Enable the deploy-tweaks script:

   mkdir -p ~oneadmin/remotes/vmm/kvm/deploy-tweaks.d
   cd ~oneadmin/remotes/vmm/kvm/deploy-tweaks.d
   ln -s ../deploy-tweaks.d.example/resizeCpuMem.py resizeCpuMem.py
   cd -
   

2. Install the helper hook:

   cp addon-storpool/hooks/resizeCpuMem.sh ~oneadmin/remotes/hooks/resizeCpuMem.sh
   onehook create addon-storpool/misc/resizeCpuMem.hook
   chown -R oneadmin.oneadmin ~oneadmin/remotes
   

3. Add protected variables:

   echo "VM_RESTRICTED_ATTR = \"T_VCPU_MAX\"" >>/etc/one/oned.conf
   echo "VM_RESTRICTED_ATTR = \"T_VCPU_NEW\"" >>/etc/one/oned.conf
   echo "VM_RESTRICTED_ATTR = \"T_CPU_SHARES\"" >>/etc/one/oned.conf
   echo "VM_RESTRICTED_ATTR = \"T_MEMORY_MAX\"" >>/etc/one/oned.conf
   echo "VM_RESTRICTED_ATTR = \"T_MEMORY_NEW\"" >>/etc/one/oned.conf
   
   systemctl restart opennebula
   

Configuration

To trigger the reconfiguration of the domain XML:

• Set T_VCPU_MAX to enable VCPU hotplug.

• Set T_MEMORY_MAX to enable Memory hotplug.

Usage

After a VM is restarted and the new domain XML configuration is in place it is possible to change the number of VCPUs and the size of the VM Memory.

VCPU change

• Set T_CPU_SHARES to the new value (this is the CPU element in the VM/CPU tab).

• Set T_VCPU_NEW to the desired number of VCPUs.

On success, the relevant VM elements will be updated ant the T_VCPU_NEW variable will be deleted.

Memory change

• Set T_MEMORY_NEW to the desired new size (in MiB).

On success, the relevant VM elements will be updated ant the T_MEMORY_NEW variable will be deleted.

API

Using one.vm.update API call all variables could be set in a single call.