Welcome to the most active Linux Forum on the web.
Go Back > Forums > Linux Forums > Linux - Newbie
User Name
Linux - Newbie This Linux forum is for members that are new to Linux.
Just starting out and have a question? If it is not in the man pages or the how-to's this is the place!


  Search this Thread
Old 11-06-2007, 02:34 PM   #1
Registered: Feb 2007
Posts: 197

Rep: Reputation: 30
virtual address space question


I am checking about memory issue document in the following link.

When they say 4 GB virtual address space, does it mean swap space? Please let me know.

thanks in advance
Old 11-06-2007, 03:26 PM   #2
Registered: Jun 2001
Location: UK
Distribution: Gentoo, RHEL, Fedora, Centos
Posts: 43,417

Rep: Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985Reputation: 1985
no, it's not any specific form of memory, RAM chips, swap on a disk etc... it's an abstraction of whatever physical memory resources you have, 64gb of physical memory or 4gb of memory and a whopping great swap disk... That article actually gives a very very good overview of what you're asking in the first place.

Last edited by acid_kewpie; 11-06-2007 at 03:29 PM.
Old 11-06-2007, 08:18 PM   #3
LQ Guru
Registered: Feb 2004
Location: SE Tennessee, USA
Distribution: Gentoo, LFS
Posts: 10,715
Blog Entries: 4

Rep: Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951Reputation: 3951
When any program runs, in any virtual-memory-based operating system (such as Unix or Linux or OS/X or Windows or IBM MVS or .. .. ..) it has a perspective of "main memory" that never matches the physical reality.

Each program .. every program .. "sees" no other program other than itself. "All of memory, as far as it can see," is its own private play-pen.

The reality, known only to the operating system, is that "memory is, in fact, an intensely-shared resource." But the only part of the system which can actually know or appreciate that fact is "the operating system," because only the operating system is ever able to know how physical memory is actually being allocated.

Every user-land program is (entirely without its knowledge or consent...) obliged to view "memory" through a hall-of-mirrors.

And what is this "view, as seen by a user-land program, through this 'hall of mirrors' that you speak of?" It is that "'memory' is no larger than 4 gigabytes, and it contains exactly what you think it does, and nothing more." Period. That is what your textbook is referring to.

Yes, indeed... that illusion, artfully pretending to be (and, from the perspective of the user-land program, indeed, being!) "reality."

Never mind what "the physical reality" is! It does not matter, after all, because a user-land program will never knows anything about what "the physical reality" might be: nor does it care.

Last edited by sundialsvcs; 11-06-2007 at 08:19 PM.


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
get the virtual address of I/O Space stz Programming 1 11-02-2006 10:44 AM
how to find physical address of kernel virtual address kushneeraj Programming 0 10-20-2006 07:29 PM
API for mapping Physical Address to Virtual Address Lakshman_smt Linux - Software 2 10-15-2006 09:08 PM
Memory Mapping (same physical address = virtual address) Linux - Kernel 7 07-24-2006 11:13 PM
Increasing virtual address space mhl Linux - Newbie 1 09-07-2005 10:29 AM > Forums > Linux Forums > Linux - Newbie

All times are GMT -5. The time now is 03:26 AM.

Main Menu
Write for LQ is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration