Patent ID: 8261267

Claim:
A virtual machine monitor to monitor virtual machines running on a computer system which runs a plurality of virtual machines by managing relation between a physical memory and a plurality of virtual memories, the virtual machine monitor comprising: a mapping data generator to determine a virtual page number capable of identifying a virtual page of a virtual memory where an executable code in an object file of a guest OS executed on a virtual machine is mapped; a virtual page manager to manage a virtual page record including: the virtual page number, a first object ID capable of uniquely identifying a part of the object file corresponding to the virtual page number, and a detection flag indicative of existence of another virtual page record containing a second object ID identical with the first object ID, and wherein the virtual page manager sets the detection flag without comparing the part identified by the second object ID with the part identified by the first object ID upon the computer system starting the virtual machine; a machine page manager to manage a machine page record including: the first object ID, and a machine page number capable of identifying a machine page of the physical memory; a sharable page detector to determine, upon first accessing an access page of the virtual memory, whether a detection flag of the virtual page record containing a virtual page number of the access page indicates existence of another virtual page record containing the second object ID identical with the first object ID, and determine, when the detection flag indicates existence of another virtual page record containing the second object ID identical with the first object ID, whether a machine page number of the machine page record containing the second object ID has been set; and a page mapper to map a set machine page number to the virtual page number of the access page upon determining that the machine page number has been set.