Virtual memory pdf. Virtual Memory Virtual memory is the technique of using secondary storage such as disks to enter the apparent size of accessible memory beyond its actual physical size. Thus we can have large virtual memory on a small physical memory. Virtual memory is implemented by employing a memory-management unit (MMU) to translate every logical address reference into a physical address reference as shown in fig 1. Virtual memory The conceptual separation of user logical memory from physical memory. With one clean mechanism, virtual memory provides three important capabilities. . The MMU is imposed between the CPU and the physical Chapter 9: Virtual Memory Background Demand Paging Copy-on-Write Page Replacement Allocation of Frames Thrashing Memory-Mapped Files Allocating Kernel Memory Other Considerations Operating-System Examples Silberschatz, Galvin and Gagne ©2009 ¢ The contents of the array on disk are cached in physical memory (DRAM cache) § These cache blocks are called pages (size is P = 2p bytes) Virtual memory Virtual memory Virtual addressing allows us to introduce the idea of virtual memory Already have valid or invalid page translations; introduce “non-resident” designation and put such pages on a non-volatile backing store Processes access non-resident memory just as if it were “the real thing” Virtual memory – separation of user logical memory from physical memory As perceived by users; that programs exist in contiguous memory Abstracts physical memory: need not worry about memory requirements Only part of the program needs to be in memory for execution Logical address space can therefore be much larger than physical address space Virtual memory is an elegant interaction of hardware exceptions, hardware address translation, main memory, disk files, and kernel software that provides each process with a large, uniform, and private address space. qpiwj ssr igxpbn ojwpyo ncv phf yzbbt xoxqnnnx aurc igbs
26th Apr 2024