Memory Sharing in Virtualization

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Memory bubble: The system actively reclaims the physical memory that the virtual machine does not use temporarily, and allocates it to the virtual machine that needs to reuse the memory. Recycling and allocation of memory are performed dynamically by the system, and applications on the virtual machine are unaware. The total amount of allocated memory used by all virtual machines on the entire physical server cannot exceed the total amount of physical memory of the server.

Memory swap: virtualize external storage into memory for virtual machine use, and store temporarily unused data on the virtual machine on external storage. When the system needs to use these data, it exchanges with the data reserved in the memory.

Memory sharing: Multiple virtual machines share memory pages with the same data content.