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Unformatted text preview: a by associating it with an object on disk, a process known as memory mapping. Areas can be mapped to one of two types of objects: 1. Regular ﬁle in the Unix ﬁlesystem: An area can be mapped to a contiguous section of a regular disk ﬁle, such as an executable object ﬁle. The ﬁle section is divided into page-sized pieces, with each piece containing the initial contents of a virtual page. Because of demand paging, none of these virtual pages is actually swapped into physical memory until the CPU ﬁrst touches the page (i.e., issues a virtual address that falls within that page’s region of the address space). If the area is larger than the ﬁle section, then the area is padded with zeros. 2. Anonymous ﬁle: An area can also be mapped to an anonymous ﬁle, created by the kernel, that contains all binary zeros. The ﬁrst time the CPU touches a virtual page in such an area, the kernel ﬁnds an appropriate victim page in physical memory, swaps out the victim page if it is dirty, overwrites the victim page with binary zeros, and updates the page table to mark the page as resident. No...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.
- Spring '10
- The American