An Overview of the Virtual Memory Xinu Project
Douglas E. Comer, James N. Griffioen · Purdue e-Pubs (Purdue University System) · 1990
The Virtual Memory Xinll Projecl investigates a new model of virtual memory in which dedicated, large-memory machines serve as backing store (page servers) for virtual memory sySlems operating on a sel of (heterogeneous) clienls.The dedicated page server allows sharing of lhe large physical memory resource and provides fast access to data.This paper gives a brief overview of the Vinual Memory Xinu research project It outlines Lhe new virtual memory model used, Lhe project's goals.a proloLype design and implementation, and experimental resulls obtained from the prololype.1. Background virtual memory operating sySlems provide mechanisms lhal allow programs requiring large amounls of memory La execute on a wide range of architectures regardless of the computer's physical memory size.This ability aids the development of portable code by allowing programmers 10 design and implemenl programs independent of the physical memory size available on the underlying machine.When user programs exhausl all available local physical memory, the operating system writes blocks of physical memory to backing sLOrage.The virtual memory sySlem laler retrieves lhe blocks of memory from lhe disk on demand.Most convemional virlual memory operating syslems use magnetic disks for backing slorage S .Magnetic disks provide high data transfer ralcs, large stornge capacily, and the abilily to randomly access dnta, making lhem an appealing backing storage medium.The operating system usually reserves a fixed size region of the disk for backing storage and writes blocks of data directly to thal region (i.e.no•2• additional file structure or other organizational structure is imposed on !.he raw storage provided by the disk)I,S.6.More recent virtual memory systems have added a level of abstraction to the paging paradigm.