Which virtual machines support dynamic RAM sizing?

Question

Virtualization

In addition to hyper-v
I'm interested in installing windows XP on virtual machines, and so that RAM is spent on maintaining virtual machines as needed in the RAM itself (dynamic amount of allocated RAM)

Answer 1

It seemed to me that in Hyper-V the implementation of dynamic memory requires support for hot-add memory from the OS? And, accordingly, XP is in the air...
In VMWare ESXi, in addition to dynamically allocated memory for virtual machines (the "ballooning" mechanism differs from Hyper-V and works on XP), there are also deduplication and memory compression features.