Virtual Swap Space in SunOS

The concept of swap space in SunOS has been extended by the abstraction of a "virtual swap file system", which allows the system to treat main memory as if it were backing store. Further, this abstraction allows for more intelligent choices to be made about swap space allocation than in the current system. This paper contrasts the existing mechanisms and their limitations with the modifications made to implement virtual swap space. 1. Introduction SunOS provides a unified set of abstractions and interfaces for interacting with virtual memory (VM) facilities both from user programs and from within the kernel. One of the major features of this architecture is that address spaces are constructed out of mappings to virtual memory objects. These mappings cause main memory pages to cache the contents of the virtual memory objects and each physical page is named by the VM object that backs it. [Gingell1987] One common type of virtual memory object is an ordinary file. Establishing a mapping ..