Physical and virtualized host memory

In a nonvirtual environment, the operating system assumes it owns all physical memory available. When an application starts, it uses interfaces provided by the OS to allocate or release virtual memory pages during the execution. Virtual memory is a technique used in most operating systems, and is supported by almost all modern CPUs. Virtual memory creates a uniform virtual address space for applications and allows the OS and hardware to handle the address translation between the virtual and physical address space. This technique adapts the execution environment to support large address spaces, process protection, file mapping, and swapping in modern computer systems.

In a vSphere environment, the VMware virtualization layer creates a contiguous addressable memory space for the virtual machine when it is started. The allocated memory space is configured when the virtual machine is created and has the same properties as the virtual address space. This configuration allows the hypervisor to run multiple virtual machines simultaneously while protecting the memory of each virtual machine from being accessed by others.

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