source: final-preps/aboutsbus.xml@ 9a83e07

Last change on this file since 9a83e07 was bf8c11f, checked in by Jim Gifford <clfs@…>, 19 years ago

r627@server (orig r625): jim | 2005-10-31 12:59:34 -0800
Import of Cross-LFS Book

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File size: 2.5 KB
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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
3 "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 %general-entities;
6]>
7
8<sect1 id="ch-final-preps-aboutsbus">
9 <?dbhtml filename="aboutsbus.html"?>
10
11 <title>About SBUs</title>
12
13 <para>TO BE REWRITTEN</para>
14
15 <!--
16 <para>Many people would like to know beforehand approximately how long
17 it takes to compile and install each package. Because Linux From
18 Scratch can be built on many different systems, it is impossible to
19 provide accurate time estimates. The biggest package (Glibc) will
20 take approximately 20 minutes on the fastest systems, but could take
21 up to three days on slower systems! Instead of providing actual times,
22 the Static Build Unit (SBU) measure will be
23 used instead.</para>
24
25 <para>The SBU measure works as follows. The first package to be compiled
26 from this book is the statically-linked Binutils in <xref
27 linkend="chapter-temporary-tools"/>. The time it takes to compile
28 this package is what will be referred to as the Static Build Unit
29 or SBU. All other compile times will be expressed relative to this
30 time.</para>
31
32 <para>For example, consider a package whose compilation time is 4.5
33 SBUs. This means that if a system took 10 minutes to compile and
34 install the static Binutils, it will take
35 <emphasis>approximately</emphasis> 45 minutes to build this example
36 package. Fortunately, most build times are shorter than the one
37 for Binutils.</para>
38
39 <para>Please note that if the system compiler on the host is GCC-2.x based, the
40 SBUs listed may be somewhat understated. This is because the SBU is
41 based on the very first package, compiled with the old GCC, while the
42 rest of the system is compiled with the newer GCC-&gcc-version; (which is
43 known to be approximately 30 percent slower). SBUs are also not
44 highly accurate for Symmetric Multi-Processor (SMP)-based machines.</para>
45
46 <para>In general, SBUs are not entirely accurate because they depend on many
47 factors, including the host system's version of GCC. Note that on Symmetric
48 Multi-Processor (SMP)-based machines, SBUs are even less accurate. They are
49 provided here to give an estimate of how long it might take to install a
50 package, but the numbers can vary by as much as dozens of minutes in some
51 cases.</para>
52
53 <para>To view actual timings for a number of specific machines, we recommend
54 <ulink url="&lfs-root;~bdubbs/"/>.</para>
55 -->
56
57</sect1>
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