DOCUMENT ID: 1203-02 SYNOPSIS: Features of the SunOS Virtual Memory OS RELEASE: 2.4 PRODUCT: Solaris KEYWORDS: virtual memory process page physical vnodes DESCRIPTION: Features of the SunOS Virtual Memory. SOLUTION: * A process's (virtual) address space is mapped onto objects in virtual memory. * Each page in virtual memory is backed by some physical storage, either disk or main memory. * A page of a process's address space can only map to one physical object. * A physical page in any given object may be mapped by many different process pages. Shared Libs would be an example. * The virtual memory system operates on pages rather than segments in order to provide efficient copy-on-write facilities. * These physical objects are represented to the kernel by virtual nodes (vnodes). Other operating systems have been segment-oriented (text, data, and stack) rather than page-oriented. By using a page-oriented system, a separate copy of a page for a process is only necessary for the page being modified. This is only necessary if the page is mapped to private access rather than shared. A vnode is a file system-independent inode. It is used to identify an object such as a local file, a remote file, or a device in kernel memory. DATE APPROVED: 10/10/95