SEB070017 - TUTORIAL 4

Tutorial 4 - SEB070017

NG
CHI BENG

 

The key to using memory efficiently is virtual
memory management. Consider both Windows  and a UNIX/Linux operating system.
Compare and contrast how each implements virtual memory. Describe how each one
handles page faults, page sizes and how it reconciles thrashing issues. Cite
your sources.

 

 

Windows	UNIX/Linux
Windows is the most prominent proprietary operating system	Linux is the most prominent operating system that is free software
A pagefile is allocated on disk, for less frequently accessed objects in memory, leaving more RAM available to actively used objects	Most hard drive installations of Linux utilize a "swap partition", where the disk space allocated for paging is separate from general data, and is used strictly for paging operations
Windows must boot from a primary partition	Linux can boot from either a primary partition or a logical partition inside an extended partition
Windows must boot from the first hard disk.	Linux can boot from any hard disk in the computer.
Windows allows programs to store user information (files and settings) anywhere. This makes it impossibly hard to backup user data files and settings and to switch to a new computer.	In contrast, Linux stores all user data in the home directory making it much easier to migrate from an old computer to a new one. If home directories are segregated in their own partition, you can even upgrade from one version of Linux to another without having to migrate user data and settings.
Only those parts of the program and data that are currently in active use need to be held in physical RAM. Other parts are then held in a swap file (in Windows 95/98/ME:) or page file (in Windows NT, Windows 2000 and XP: pagefile.sys). When a program tries to access some address that is not currently in physical RAM, it generates an interrupt, called a Page Fault. This asks the system to retrieve the 4 KB page containing the address from the page file (or in the case of code possibly from the original program file). This — a valid page fault — normally happens quite invisibly. Sometimes, through program or hardware error, the page is not there either. The system then has an ‘Invalid Page Fault’ error. This will be a fatal error if detected in a program: if it is seen within the system itself (perhaps because a program sent it a bad request to do something), it may manifest itself as a ‘blue screen’ failure with a STOP code: consult the page on STOP Messages on this site.	Pages from a process are swapped The process becomes runnable and attempts to access a swapped page The page is faulted back into memory (most likely forcing some other processes' pages to be swapped out) A short time later, the page is swapped out again
Win32-based operating system, such as Windows 9x, NT, ReactOS, use the system function GetSystemInfo() from kernel32.dll. #include <stdio.h> #include <windows.h> int main() { SYSTEM_INFO si; GetSystemInfo(&si); printf("The page size for this system is %u bytes\n", si.dwPageSize); return 0; }	UNIX and POSIX-based systems use the system function sysconf(), as illustrated in the following example written in the C programming language. #include <stdio.h> #include <unistd.h> // sysconf(3) int main() { printf("The page size for this system is %ld bytes\n", sysconf(_SC_PAGESIZE)); //_SC_PAGE_SIZE is OK too. return 0; }
Windows has two main lines. The older flavors are referred to as "Win9x" and consist of Windows 95, 98, 98SE and Me. The newer flavors are referred to as "NT class" and consist of Windows NT3, NT4, 2000, XP and Vista. Going back in time, Windows 3.x preceded Windows 95 by a few years. And before that, there were earlier versons of Windows, but they were not popular. Microsoft no longer supports Windows NT3, NT4, all the 9x versions and of course anything older. Support for Windows 2000 is partial (as of April 2007).	The flavors of Linux are referred to as distributions (often shortened to "distros"). All the Linux distributions released around the same time frame will use the same kernel (the guts of the Operating System). They differ in the add-on software provided, GUI, install process, price, documentation and technical support. Both Linux and Windows come in desktop and server editions.
The Windows GUI has changed from Windows 3.1 to Windows 95 (drastically) to Windows 2000 (slightly) to Windows XP (fairly large) and is slated to change again with the next version of Windows, the one that will replace XP. Windows XP has a themes feature that offers some customization of the look and feel of the GUI.	Linux typically provides two GUIs, KDE and Gnome. See a screen shot of Lycoris and Lindows in action from the Wal-Mart web site. The lynucs.org web site has examples of many substantially different Linux GUIs. Of the major Linux distributions, Lindows has made their user interface look more like Windows than the others. Here is a screen shot of Linux made to look like Windows XP. Then too, there is XPde for Linux which really makes Linux look like Windows. Quoting their web site "It's a desktop environment (XPde) and a window manager (XPwm) for Linux. It tries to make easier for Windows XP users to use a Linux box."

 

References:

1.http://en.wikipedia.org/wiki/Comparison_of_Windows_and_Linux#Installation

2.


http://rangit.com/operating-systems/8-major-differences-between-linux

 

- and-windows/

3. http://www. aumha.
org/win5/a/ xpvm.php

4.


http://www.michaelhorowitz.com/Linux.vs.Windows.html

5. www. how stuff works. com