Dynamic Allocation of External Page Tables in the AIX Operating System
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
The AIX* operating system implements its virtual memory using paged segmentation. A segment, always a 256 Mb partition of address space that is contiguous in virtual space, is used to represent an object, such as an ASCII file, a program, or shared memory. The two general types of segments are mapped file and working storage. One of the Virtual Memory Manager (VMM) data structures associated with each segment is an External Page Table (XPT). The XPT contains one entry for every virtual page in the segment. Each entry describes the characteristics of its corresponding page, such as its level of protection and its location on hard disk. As users create files and execute programs, XPT entries are allocated on demand and released when no longer needed.