For a vCPU, shares, reservation, and limit parameters can be configured:
- Shares: This parameter allows you to prioritize access to resources during resource contention. Shares determine how much CPU power in GHz will be provided to a VM.
- Reservation: This is used to specify the minimum CPU power in GHz guaranteed for a VM, and you can't reserve more CPU cycles than ESXi is capable of delivering. The host must have enough physical CPU capacity to satisfy the reservation; otherwise, the VM won't be able to power on.
- Limit: This is used to prevent a VM from accessing additional CPU power in GHz, even if they are available. The VM won't use more CPU cycles than specified in the limit.
To configure shares, reservation, and limit CPU parameters, follow these steps:
- Right-click the VM to configure and select Edit Settings
- Access the Virtual Hardware tab and expand the CPU item
- Configure the parameters you need, and then click OK to confirm:
To improve resource management, CPU configuration can be enhanced by enabling additional components and parameters:
- Hyperthreading: This is a technology that allows a single physical processor core to behave like two logical processors. With this technology, a single processor core can execute two independent threads simultaneously, improving performance.
- CPU affinity: This is a configuration that assigns a specific VM to a specific physical CPU core and can be used for compliance to license requirements. CPU affinity should be used carefully because it can introduce potential issues, such as interfering with the ESXi host's ability to meet the reservation and shares that have been specified for a VM.