Virtual machine system, memory management method, memory management program, recording medium, and integrated circuit

A memory management method for a virtual machine system that duplicates a first virtual machine to generate one or more second virtual machines, the memory management method comprising:

• managing a memory area among one or more memory areas accessible by the first virtual machine so that after generation of the one or more second virtual machines, each of the first virtual machine and the one or more second virtual machines is permitted to perform a read access to the memory area until any virtual machine among the first virtual machine and the one or more second virtual machines performs a first write access to the memory area;
• determining whether the memory area is a specific memory area whose content before the first write access does not need to be stored based on a classification value which is a value for identifying content of memory allocation processing, when the first write access to the memory area is performed, for a subsequent access by a virtual machine other than the any virtual machine performing the first write access;
• detecting the first write access to the specific memory area;
• detecting, after the first write access to the specific memory area is detected, that the virtual machine other than the any virtual machine performing the first write access is attempting the subsequent access to the specific memory area;
• and
• (i) acquiring a new memory area, (ii) copying, into the new memory area, content of the specific memory area before the attempted subsequent access to the specific memory area by the virtual machine attempting the subsequent access to the specific memory area, and (iii) allocating the new memory area, as a target of the attempted subsequent access, to the virtual machine attempting the subsequent access to the specific memory area.

A non-transitory computer readable recording medium having stored thereon a memory management program for a virtual machine system on a computer, the virtual machine system duplicating a first virtual machine to generate one or more second virtual machines, the memory management program causing the computer to perform:

• managing a memory area among one or more memory areas accessible by the first virtual machine so that after generation of the one or more second virtual machines, each of the first virtual machine and the one or more second virtual machines is permitted to perform a read access to the memory area until any virtual machine among the first virtual machine and the one or more second virtual machines performs a first write access to the memory area;
• determining whether the memory area is a specific memory area whose content before the first write access does not need to be stored based on a classification value which is a value for identifying content of memory allocation processing, when the first write access to the memory area is performed, for a subsequent access by a virtual machine other than the any virtual machine performing the first write access;
• detecting the first write access to the specific memory area;
• detecting, after the first write access to the specific memory area is detected, that the virtual machine other than the any virtual machine performing the first write access is attempting the subsequent access to the specific memory area;
• and
• (i) acquiring a new memory area, (ii) copying, into the new memory area, content of the specific memory area before the attempted subsequent access to the specific memory area by the virtual machine attempting the subsequent access to the specific memory area, and (iii) allocating the new memory area, as a target of the attempted subsequent access, to the virtual machine attempting the subsequent access to the specific memory area.

An integrated circuit constituting a virtual machine system for duplicating a first virtual machine to generate one or more second virtual machines, the integrated circuit comprising:

• a processor;
• and
• a non-transitory memory having stored thereon executable instructions, which when executed by the processor, cause the processor to perform:
• managing a memory area among one or more memory areas accessible by the first virtual machine so that after generation of the one or more second virtual machines, each of the first virtual machine and the one or more second virtual machines is permitted to perform a read access to the memory area until any virtual machine among the first virtual machine and the one or more second virtual machines performs a first write access to the memory area;
• determining whether the memory area is a specific memory area whose content before the first write access does not need to be stored based on a classification value which is a value for identifying content of memory allocation processing, when the first write access to the memory area is performed, for a subsequent access by a virtual machine other than the any virtual machine performing the first write access;
• detecting the first write access to the specific memory area;
• detecting, after the first write access to the specific memory area is detected, that the virtual machine other than the any virtual machine performing the first write access is attempting the subsequent access to the specific memory area;
• and
• (i) acquiring a new memory area, (ii) copying, into the new memory area, content of the specific memory area before the attempted subsequent access to the specific memory area by the virtual machine attempting the subsequent access to the specific memory area, and (iii) allocating the new memory area, as a target of the attempted subsequent access, to the virtual machine attempting the subsequent access to the specific memory area.