Operating System《操作系统》ch02-Operating-System Structures-42.ppt

Solaris Modular Approach Mac OS X hybrid structure 2.8 Virtual Machines The fundamental idea behind a virtual machine is to abstract the hardware of a single computer into several different execution environments, thereby creating the illusion that each separate execution environment is running its own private computer. A virtual machine takes the layered approach to its logical conclusion. It treats hardware and the operating system kernel as though they were all hardware A virtual machine provides an interface identical to the underlying bare hardware The operating system creates the illusion of multiple processes, each executing on its own processor with its own (virtual) memory Virtual Machines (Cont.) The resources of the physical computer are shared to create the virtual machines CPU scheduling can create the appearance that users have their own processor Spooling and a file system can provide virtual card readers and virtual line printers A normal user time-sharing terminal serves as the virtual machine operator’s console Virtual Machines (Cont.) (a) Nonvirtual machine (b) virtual machine Non-virtual Machine Virtual Machine Virtual Machines (Cont.) The virtual-machine concept provides complete protection of system resources since each virtual machine is isolated from all other virtual machines. This isolation, however, permits no direct sharing of resources. A virtual-machine system is a perfect vehicle for operating-systems research and development. System development is done on the virtual machine, instead of on a physical machine and so does not disrupt normal system operation. The virtual machine concept is difficult to implement due to the effort required to provide an exact duplicate to the underlying machine VMware Architecture The Java Virtual Machine 2.9 Operating System Generation Operating systems are designed to run on any of a class of machines; the system must be configured for each specific comp