tailieunhanh - Lecture Operating system concepts (Sixth ed) - Chapter 10: Virtual memory

In chapter 7, we discussed various memory-management strategies used in computer systems. All these strategies have the same goal: to keep many processes in memory simultaneously to allow multiprogramming. However, they tend to require that an entire process be in memory before it can execute. Virtual memory is a technique that allows the execution of processes that are not completely in memory. In this chapter, we discuss virtual memory in the form of demand paging and examine its complexity and cost. | Chapter 10 Virtual Memory Background Demand Paging Process Creation Page Replacement Allocation of Frames Thrashing Operating System Examples Operating System Concepts Silberschatz Galvin and Gagne 2002 Background Virtual memory - separation of user logical memory from physical memory. Only part of the program needs to be in memory for execution. Logical address space can therefore be much larger than physical address space. Allows address spaces to be shared by several processes. Allows for more efficient process creation. Virtual memory can be implemented via Demand paging Demand segmentation Operating System Concepts Silberschatz Galvin and Gagne 2002 Demand Paging Bring a page into memory only when it is needed. Less I O needed Less memory needed Faster response More users Page is needed reference to it invalid reference abort not-in-memory bring to memory Operating System Concepts Silberschatz Galvin and Gagne 2002 ransfer of a Paged Memory to Contiguous Disk Space Operating System Concepts Silberschatz Galvin and Gagne .