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diff --git a/sag-0.6.1-www/Invisible/sag-0.6/node64.html b/sag-0.6.1-www/Invisible/sag-0.6/node64.html new file mode 100644 index 0000000..e5bf5af --- /dev/null +++ b/sag-0.6.1-www/Invisible/sag-0.6/node64.html @@ -0,0 +1,111 @@ +<!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>Allocating swap space</TITLE> +<META NAME="description" CONTENT="Allocating swap space"> +<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="tex2html1118" HREF="node65.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html1116" HREF="node59.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html1110" HREF="node63.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html1120" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html1121" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html1119" HREF="node65.html">The buffer cache</A> +<B>Up:</B> <A NAME="tex2html1117" HREF="node59.html">Memory Management</A> +<B> Previous:</B> <A NAME="tex2html1111" HREF="node63.html">Sharing swap spaces with </A> +<BR> <P> +<H1><A NAME="SECTION00650000000000000000">Allocating swap space</A></H1> + <A NAME="secswapalloc"> </A> +<P> + Some people will tell you that you should allocate twice as much + swap space as you have physical memory, but this is a bogus rule. + Here's how to do it properly: +<P> + <OL> +<LI> +<P> + Estimate your total memory needs. This is the largest amount of + memory you'll probably need at a time, that is the sum of the + memory requirements of all the programs you want to run at the + same time. This can be done by running at the same time all the + programs you are likely to ever be running at the same time. +<P> + For instance, if you want to run X, you should allocate + about 8 MB for it, gcc wants several megabytes (some + files need an unusually large amount, up to tens of + megabytes, but usually about four should do), and so on. + The kernel will use about a megabyte by itself, and the + usual shells and other small utilities perhaps a few + hundred kilobytes (say a megabyte together). There is + no need to try to be exact, rough estimates are fine, + but you might want to be on the pessimistic side. +<P> + Remember that if there are going to be several people + using the system at the same time, they are all going + to consume memory. However, if two people run the same + program at the same time, the total memory consumption + is usually not double, since code pages and shared + libraries exist only once. +<P> + The <tt>free</tt><A NAME="1924"> </A> and <tt>ps</tt><A NAME="1926"> </A> commands are useful for + estimating the memory needs. +<LI> +<P> + Add some security to the estimate in step 1. This is because + estimates of program sizes will probably be wrong, because + you'll probably forget some programs you want to run, and to + make certain that you have some extra space just in case. A + couple of megabytes should be fine. (It is better to allocate + too much than too little swap space, but there's no need to + over-do it and allocate the whole disk, since unused swap space + is wasted space; see later about adding more swap.) Also, + since it is nicer to deal with even numbers, you can round the + value up to the next full megabyte. +<LI> +<P> + Based on the computations above, you know how much memory + you'll be needing in total. So, in order to allocate + swap space, you just need to subtract the size of your + physical memory from the total memory needed, and you + know how much swap space you need. (On some versions + of UNIX, you need to allocate space for an image of the + physical memory as well, so the amount computed in step + 2 is what you need and you shouldn't do the subtraction.) +<LI> +<P> + If your calculated swap space is very much larger than your + physical memory (more than a couple times larger), you should + probably invest in more physical memory, otherwise performance + will be too low. +<P> + </OL> +<P> + It's a good idea to have at least some swap space, even if + your calculations indicate that you need none. Linux uses + swap space somewhat aggressively, so that as much physical + memory as possible can be kept free. Linux will swap out + memory pages that have not been used, even if the memory + is not yet needed for anything. This avoids waiting for + swapping when it is needed--the swapping can be done + earlier, when the disk is otherwise idle. +<P> + Swap space can be divided among several disks. This + can sometimes improve performance, depending on the + relative speeds of the disks and the access patterns + of the disks. You might want to experiment with a few + schemes, but be aware that doing the experiments + properly is quite difficult. You should not believe + claims that any one scheme is superior to any other, + since it won't always be true. +<P> +<HR><A NAME="tex2html1118" HREF="node65.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html1116" HREF="node59.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html1110" HREF="node63.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html1120" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html1121" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html1119" HREF="node65.html">The buffer cache</A> +<B>Up:</B> <A NAME="tex2html1117" HREF="node59.html">Memory Management</A> +<B> Previous:</B> <A NAME="tex2html1111" HREF="node63.html">Sharing swap spaces with </A> +<P><ADDRESS> +<I>Lars Wirzenius <BR> +Sat Nov 15 02:32:11 EET 1997</I> +</ADDRESS> +</BODY> +</HTML> |