[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[966c6512] | 2 | <!DOCTYPE section [
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[673b0d8] | 3 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 4 | %general-entities;
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| 5 | ]>
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[966c6512] | 6 | <section xmlns="http://docbook.org/docbook-ng"
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| 7 | xmlns:xlink="http://www.w3.org/1999/xlink"
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| 8 | xml:id="prepare-aboutsbus">
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| 9 | <info><title>About SBUs</title></info>
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[673b0d8] | 10 | <?dbhtml filename="aboutsbus.html"?>
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| 11 |
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| 12 | <para>Most people would like to know beforehand approximately how long it
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[55851d6] | 13 | takes to compile and install each package. But <quote>Linux from Scratch</quote> is built
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[673b0d8] | 14 | on so many different systems, it is not possible to give actual times that are
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| 15 | anywhere near accurate: the biggest package (Glibc) won't take more than
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| 16 | twenty minutes on the fastest systems, but will take something like three days
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| 17 | on the slowest -- no kidding. So instead of giving actual times, we've come up
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| 18 | with the idea of using the <emphasis>Static Binutils Unit</emphasis>
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| 19 | (abbreviated to <emphasis>SBU</emphasis>).</para>
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| 20 |
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| 21 | <para>It works like this: the first package you compile in this book is the
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| 22 | statically linked Binutils in <xref linkend="chapter-temporary-tools"/>, and the time it
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| 23 | takes to compile this package is what we call the <quote>Static Binutils
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| 24 | Unit</quote> or <quote>SBU</quote>. All other compile times will be expressed
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| 25 | relative to this time.</para>
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| 26 |
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| 27 | <para>For example, consider a particular package whose compilation time is 4.5
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| 28 | SBUs. This means that if on your system it took 10 minutes to compile and
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| 29 | install the static Binutils, then you know it will take
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| 30 | <emphasis>approximately</emphasis> 45 minutes to build this package.
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| 31 | Fortunately, most build times are much shorter than the one of Binutils.</para>
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| 32 |
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| 33 | <para>Note that if the system compiler on your host is GCC-2 based, the SBUs
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| 34 | listed may end up being somewhat understated. This is because the SBU is based
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| 35 | on the very first package, compiled with the old GCC, while the rest of the
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[223b84a] | 36 | system is compiled with the newer GCC-&gcc-version; which is known to be
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[673b0d8] | 37 | approximately 30% slower.</para>
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| 38 |
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| 39 | <para>Also note that SBUs don't work well for SMP-based machines. But if you're
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| 40 | so lucky as to have multiple processors, chances are that your system is so fast
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| 41 | that you won't mind.</para>
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| 42 |
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| 43 | <para>If you wish to see actual timings for specific machines, have a look at
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[966c6512] | 44 | <uri xlink:href="&lfs-root;~bdubbs/"/>.</para>
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[673b0d8] | 45 |
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[966c6512] | 46 | </section>
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