Method and computer system for memory management on virtual machine

A computer system comprising:

• a memory;
• a processor, coupled to the memory, wherein the processor performs an operation for memory management on a virtual machine system, the operation comprising:
• setting a first threshold value;
• setting a balloon target of a balloon driver to an allocated virtual memory size and decrementing the balloon target by a first decrement value stepwise according to a swapin/refault detecting result in a first adjustment state;
• generating the swapin/refault detecting result by detecting at least one swapin or refault event;
• stopping decrementing the balloon target according to the swapin/refault detecting result in a cool-down state;
• and
• decrementing the balloon target by a second decrement value stepwise in a second adjustment state which is after the cool-down state,
• wherein the second decrement value is less than the first decrement value, and the balloon target is not less than the first threshold value.