How is the distribution of virtual processors carried out in the VMware ESXi hypervisor?

In VMware ESXi, virtual processors (vCPU) are allocated by the hypervisor over the physical processors (pCPU) of the server. Each vCPU is a logical representation of a physical core, assigned to a virtual machine.

The hypervisor uses a CPU scheduler that dynamically allocates the runtime of physical cores among the vCPUs of all virtual machines. In this process:

• A vCPU does not necessarily correspond to a single physical core — multiple vCPUs can compete for the same core.
• The scheduler aims to ensure fair resource distribution, considering the priorities and settings of virtual machines.
• If the total number of vCPUs exceeds the number of physical cores, resource overcommitment occurs, which can impact performance.

Thus, vCPU allocation is a dynamic process managed by the ESXi scheduler, which balances the load between virtual machines and physical resources.