17.1 About Page Swapping

The virtual paging device manages all demand-paging operations for Windows, determining which pages can be saved or retrieved from disk. This device uses the virtual swap file device to read and write pages to disk. The swap file device manages the virtual memory swapping file and carries out all read and write operations requested by the paging device.

The paging device has the following services:

PageSwap_Create
PageSwap_Destroy
PageSwap_Get_Version
PageSwap_In
PageSwap_Out
PageSwap_Test_Create
PageSwap_Test_IO_Valid

The page swap device has the following services:

PageFile_Cancel
PageFile_Clean_Up
PageFile_Get_Version
PageFile_Grow_File
PageFile_Init_File
PageFile_Read_Or_Write
PageFile_Test_IO_Valid

The swap file device can use a fast disk device to access the file, or can use either MS-DOS system functions (Interrupt 21h) or ROM BIOS routines (Interrupt 13h) to carry out the read and write operations.