Microsoft Hyper-V Dynamic Memory

Dynamic Memory is a memory allocation feature for Microsoft Hyper-V which pools the host's memory and sends resources to virtual machines (VMs) that need it.  When Hyper-V Dynamic Memory is enabled, the VM declares how much memory it needs and the host  provides that quantity plus an extra amount to be  used as a buffer.

Dynamic Memory, which can be compared with Vmware’s memory overcommit feature,rebalances the host's memory in one-second intervals and allows VMs to be prioritized in terms of memory usage.