Patent ID: 8214559

Claim:
A virtual machine system disposed on one computer device including a CPU, a memory, an IO device, an IO controller, and an IO interface for connecting to the IO device and IO controller, the virtual machine system comprising: a hypervisor that generates plural virtual servers; and an operating system that is executed by each of the virtual servers individually, wherein the IO controller controls the IO interface, the IO controller being located between the IO interface and at least one of the CPU and the memory, wherein the IO controller has: a receiving unit that receives requests from the IO device to the memory; a virtual server locating unit that identifies the virtual servers corresponding to the received requests; a monitoring counter that monitors request processing status for each of the virtual servers; a threshold register set in advance for each of the virtual servers; and a priority deciding unit that compares the monitoring counter and a value of the threshold register, the priority deciding unit deciding the priority of processing of the received requests, and has a notification interface that notifies to the hypervisor the virtual server corresponding to the decided priority, wherein the monitoring counter holds credit information indicating the number of receivable requests, wherein the priority deciding unit assigns high priority to the received requests when the credit information exceeds the threshold register value, and wherein the priority deciding unit assigns low priority to the received requests when the credit information is less than the threshold register value, and wherein the hypervisor has: a register operation interface that sets the monitoring counter and the threshold register, and a request suppression interface that suppresses the requests from the virtual server notified from the IO controller.