What are pageouts ? Post: 24961

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Top Forums UNIX for Dummies Questions & Answers What are pageouts ? Post 24961 by RTM on Monday 22nd of July 2002 02:10:17 PM

07-22-2002

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In a virtual memory computer, paging is the transfer of program segments (pages) into and out of memory. Although paging is the primary mechanism for virtual memory, excessive paging is not desired (thrashing - Excessive paging in a virtual memory computer. If programs are not written to run in a virtual memory environment, the operating system may spend excessive amounts of time swapping program pages in and out of the disk.

The goal of virtual memory is to increase internal memory capacity, not to waste time reloading program segments over and over. However, a well-designed virtual memory system tracks page usage and prevents the most-often-used modules from being swapped to disk.)

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LEARN ABOUT BSD

swapon

SWAPON(8)						      System Manager's Manual							 SWAPON(8)

NAME

       swapon - specify additional device for paging and swapping

SYNOPSIS

       swapon -a
       swapon name ...

DESCRIPTION

       Swapon  is  used to specify additional devices on which paging and swapping are to take place.  The system begins by swapping and paging on
       only a single device so that only one disk is required at bootstrap time.  Calls to swapon normally occur in the system multi-user initial-
       ization file /etc/rc making all swap devices available, so that the paging and swapping activity is interleaved across several devices.

       Normally, the -a argument is given, causing all devices marked as ``sw'' swap devices in /etc/fstab to be made available.

       The  second  form gives individual block devices as given in the system swap configuration table.  The call makes only this space available
       to the system for swap allocation.

SEE ALSO

       swapon(2), init(8)

FILES

       /dev/[ru][pk]?b	   normal paging devices

BUGS

       There is no way to stop paging and swapping on a device.  It is therefore not possible to make use of devices which may be dismounted  dur-
       ing system operation.

       swapon is not implemented in 2.11BSD.

4th Berkeley Distribution					 November 17, 1996							 SWAPON(8)