What term describes the process that allows a hypervisor to reclaim unused memory from virtual machines?

The term that describes the process allowing a hypervisor to reclaim unused memory from virtual machines is known as memory ballooning. This technique involves a "balloon" driver installed within the guest operating system of the virtual machine. When the hypervisor detects that it needs to free up memory resources, it instructs the balloon driver to allocate memory within the guest OS. The balloon driver then "inflates" by consuming memory, which forces the OS to release memory that can be returned to the hypervisor. This process is essential in optimizing the overall memory utilization in environments where multiple virtual machines are hosted.

Other concepts mentioned, such as memory optimization, memory overcommitment, and memory allocation, relate to memory management in virtualized environments but do not specifically refer to the same reclaiming process as memory ballooning does. Memory optimization generally refers to strategies for improving usage efficiency overall; memory overcommitment refers to allocating more memory to virtual machines than the physical host actually has, potentially leading to performance trade-offs; while memory allocation simply describes the process of assigning memory resources to virtual machines without addressing reclaiming unused memory.