System, method and program to manage virtual memory allocated by a virtual machine control program

A computer system for allocating virtual memory to a virtual machine control program and a plurality of virtual machines, each of said virtual machines having an allocation of virtual private memory divided into working memory, cache memory and swap memory, said computer system comprising:

• means for determining that said virtual machine control program needs additional virtual memory allocation, and in response, making respective requests to said virtual machines to convert some of their respective working memory and/or cache memory to swap memory;
• and
• said virtual machines including means for complying with said respective requests to convert some of their respective working memory and/or cache memory to swap memory.

A method for managing virtual memory allocated by a virtual machine control program to a plurality of virtual machines, each of said virtual machines having an allocation of virtual private memory divided into working memory, cache memory and swap memory, said method comprising the steps of:

• the virtual machine control program determining that it needs less virtual memory allocation than currently allocated to said virtual machine control program, and in response, the virtual machine control program making respective requests to said virtual machines to convert some of their respective swap memory to working memory and/or cache memory.