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diff --git a/sag-0.6.1-www/sag-0.6.1.html/c1450.html b/sag-0.6.1-www/sag-0.6.1.html/c1450.html new file mode 100644 index 0000000..6be696d --- /dev/null +++ b/sag-0.6.1-www/sag-0.6.1.html/c1450.html @@ -0,0 +1,264 @@ +<!DOCTYPE HTML PUBLIC "-//Norman Walsh//DTD DocBook HTML 1.0//EN"> +<HTML +><HEAD +><TITLE +>Memory Management</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet"><LINK +REL="HOME" +TITLE="The Linux System Administrators' Guide" +HREF="book1.html"><LINK +REL="PREVIOUS" +TITLE="Allocating disk space" +HREF="x1384.html"><LINK +REL="NEXT" +TITLE="Creating a swap space" +HREF="x1466.html"></HEAD +><BODY +BGCOLOR="#FFFFFF" +TEXT="#000000" +><DIV +CLASS="NAVHEADER" +><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>The Linux System Administrators' Guide</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="x1384.html" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +></TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="x1466.html" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="CHAPTER" +><H1 +><A +NAME="MEMORY-MANAGEMENT" +>Chapter 5. Memory Management</A +></H1 +><DIV +CLASS="TOC" +><DL +><DT +><B +>Table of Contents</B +></DT +><DT +><A +HREF="c1450.html#AEN1456" +>What is virtual memory?</A +></DT +><DT +><A +HREF="x1466.html" +>Creating a swap space</A +></DT +><DT +><A +HREF="x1495.html" +>Using a swap space</A +></DT +><DT +><A +HREF="x1529.html" +>Sharing swap spaces with other operating systems</A +></DT +><DT +><A +HREF="x1532.html" +>Allocating swap space</A +></DT +><DT +><A +HREF="x1551.html" +>The buffer cache</A +></DT +></DL +></DIV +><BLOCKQUOTE +><P +>“Minnet, jag har tappat mitt minne, + är jag svensk eller finne, kommer inte ihåg...” + (Bosse Österberg) + </P +></BLOCKQUOTE +><P +> This section describes the Linux memory management + features, i.e., virtual memory and the disk buffer cache. + The purpose and workings and the things the system administrator + needs to take into consideration are described.</P +><DIV +CLASS="SECT1" +><H1 +CLASS="SECT1" +><A +NAME="AEN1456" +>What is virtual memory?</A +></H1 +><P +>Linux supports <I +CLASS="GLOSSTERM" +>virtual memory</I +>, that + is, using a disk as an extension of RAM so that the effective + size of usable memory grows correspondingly. The kernel will + write the contents of a currently unused block of memory to the + hard disk so that the memory can be used for another purpose. + When the original contents are needed again, they are read back + into memory. This is all made completely transparent to the + user; programs running under Linux only see the larger amount of + memory available and don't notice that parts of them reside on + the disk from time to time. Of course, reading and writing the + hard disk is slower (on the order of a thousand times slower) + than using real memory, so the programs don't run as fast. + The part of the hard disk that is used as virtual memory is + called the <I +CLASS="GLOSSTERM" +>swap space</I +>.</P +><P +>Linux can use either a normal file in the filesystem or a + separate partition for swap space. A swap partition is + faster, but it is easier to change the size of a swap file + (there's no need to repartition the whole hard disk, and + possibly install everything from scratch). When you know how + much swap space you need, you should go for a swap partition, + but if you are uncertain, you can use a swap file first, use + the system for a while so that you can get a feel for how much + swap you need, and then make a swap partition when you're + confident about its size.</P +><P +>You should also know that Linux allows one to use several swap + partitions and/or swap files at the same time. This means + that if you only occasionally need an unusual amount of swap space, + you can set up an extra swap file at such times, instead of + keeping the whole amount allocated all the time.</P +><P +>A note on operating system terminology: computer science usually + distinguishes between swapping (writing the whole process out to + swap space) and paging (writing only fixed size parts, usually + a few kilobytes, at a time). Paging is usually more efficient, + and that's what Linux does, but traditional Linux terminology + talks about swapping anyway. + + <A +NAME="AEN1464" +HREF="#FTN.AEN1464" +>[1]</A +> + </P +></DIV +></DIV +><H3 +>Notes</H3 +><TABLE +BORDER="0" +CLASS="FOOTNOTES" +WIDTH="100%" +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="5%" +><A +NAME="FTN.AEN1464" +HREF="c1450.html#AEN1464" +>[1]</A +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="95%" +><P +>Thus quite needlessly annoying a + number of computer scientists something horrible. + </P +></TD +></TR +></TABLE +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="x1384.html" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="book1.html" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="x1466.html" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>Allocating disk space</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +> </TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>Creating a swap space</TD +></TR +></TABLE +></DIV +></BODY +></HTML +>
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