| 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
|
|---|
| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
|
|---|
| 3 | <!ENTITY % general-entities SYSTEM "../general.ent">
|
|---|
| 4 | %general-entities;
|
|---|
| 5 | ]>
|
|---|
| 6 | <sect1 id="prepare-aboutsbus">
|
|---|
| 7 | <title>About SBUs</title>
|
|---|
| 8 | <?dbhtml filename="aboutsbus.html"?>
|
|---|
| 9 |
|
|---|
| 10 | <para>Most people would like to know beforehand approximately how long it
|
|---|
| 11 | takes to compile and install each package. But "Linux from Scratch" is built
|
|---|
| 12 | on so many different systems, it is not possible to give actual times that are
|
|---|
| 13 | anywhere near accurate: the biggest package (Glibc) won't take more than
|
|---|
| 14 | twenty minutes on the fastest systems, but will take something like three days
|
|---|
| 15 | on the slowest -- no kidding. So instead of giving actual times, we've come up
|
|---|
| 16 | with the idea of using the <emphasis>Static Binutils Unit</emphasis>
|
|---|
| 17 | (abbreviated to <emphasis>SBU</emphasis>).</para>
|
|---|
| 18 |
|
|---|
| 19 | <para>It works like this: the first package you compile in this book is the
|
|---|
| 20 | statically linked Binutils in <xref linkend="chapter-temporary-tools"/>, and the time it
|
|---|
| 21 | takes to compile this package is what we call the <quote>Static Binutils
|
|---|
| 22 | Unit</quote> or <quote>SBU</quote>. All other compile times will be expressed
|
|---|
| 23 | relative to this time.</para>
|
|---|
| 24 |
|
|---|
| 25 | <para>For example, consider a particular package whose compilation time is 4.5
|
|---|
| 26 | SBUs. This means that if on your system it took 10 minutes to compile and
|
|---|
| 27 | install the static Binutils, then you know it will take
|
|---|
| 28 | <emphasis>approximately</emphasis> 45 minutes to build this package.
|
|---|
| 29 | Fortunately, most build times are much shorter than the one of Binutils.</para>
|
|---|
| 30 |
|
|---|
| 31 | <para>Note that if the system compiler on your host is GCC-2 based, the SBUs
|
|---|
| 32 | listed may end up being somewhat understated. This is because the SBU is based
|
|---|
| 33 | on the very first package, compiled with the old GCC, while the rest of the
|
|---|
| 34 | system is compiled with the newer GCC-&gcc-version; which is known to be
|
|---|
| 35 | approximately 30% slower.</para>
|
|---|
| 36 |
|
|---|
| 37 | <para>Also note that SBUs don't work well for SMP-based machines. But if you're
|
|---|
| 38 | so lucky as to have multiple processors, chances are that your system is so fast
|
|---|
| 39 | that you won't mind.</para>
|
|---|
| 40 |
|
|---|
| 41 | <para>If you wish to see actual timings for specific machines, have a look at
|
|---|
| 42 | <ulink url="&lfs-root;~bdubbs/"/>.</para>
|
|---|
| 43 |
|
|---|
| 44 | </sect1>
|
|---|
