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diff --git a/sag-0.6.1-www/Invisible/sag-0.6/node60.html b/sag-0.6.1-www/Invisible/sag-0.6/node60.html new file mode 100644 index 0000000..39ad118 --- /dev/null +++ b/sag-0.6.1-www/Invisible/sag-0.6/node60.html @@ -0,0 +1,69 @@ +<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> +<!--Converted with LaTeX2HTML 96.1-h (September 30, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds --> +<HTML> +<HEAD> +<TITLE>What is virtual memory?</TITLE> +<META NAME="description" CONTENT="What is virtual memory?"> +<META NAME="keywords" CONTENT="sag"> +<META NAME="resource-type" CONTENT="document"> +<META NAME="distribution" CONTENT="global"> +<LINK REL=STYLESHEET HREF="sag.css"> +</HEAD> +<BODY LANG="EN" > + <A NAME="tex2html1070" HREF="node61.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html1068" HREF="node59.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html1062" HREF="node59.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html1072" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html1073" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html1071" HREF="node61.html">Creating a swap space</A> +<B>Up:</B> <A NAME="tex2html1069" HREF="node59.html">Memory Management</A> +<B> Previous:</B> <A NAME="tex2html1063" HREF="node59.html">Memory Management</A> +<BR> <P> +<H1><A NAME="SECTION00610000000000000000">What is virtual memory?</A></H1> +<P> + Linux supports <b>virtual memory</b>, 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 <b>swap space</b>. +<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> + 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> + 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="tex2html26" HREF="footnode.html#1820"><IMG ALIGN=BOTTOM ALT="gif" SRC="./foot_motif.gif"></A> +<P> +<HR><A NAME="tex2html1070" HREF="node61.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html1068" HREF="node59.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html1062" HREF="node59.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html1072" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html1073" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html1071" HREF="node61.html">Creating a swap space</A> +<B>Up:</B> <A NAME="tex2html1069" HREF="node59.html">Memory Management</A> +<B> Previous:</B> <A NAME="tex2html1063" HREF="node59.html">Memory Management</A> +<P><ADDRESS> +<I>Lars Wirzenius <BR> +Sat Nov 15 02:32:11 EET 1997</I> +</ADDRESS> +</BODY> +</HTML> |