Ignore:
Timestamp:
08/08/2004 02:10:22 AM (20 years ago)
Author:
Gerard Beekmans <gerard@…>
Branches:
6.0
Children:
6e41459
Parents:
843710f
Message:

Completed global edits for upcoming 6.0 release

git-svn-id: ​http://svn.linuxfromscratch.org/LFS/branches/testing/BOOK@3998 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

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  • chapter04/aboutsbus.xml

    r843710f r78349b7  
    88<?dbhtml filename="aboutsbus.html"?>
    99
    10 <para>Most people would like to know beforehand approximately how long it
    11 takes to compile and install each package. But <quote>Linux from Scratch</quote> 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>
     10<para>Most people would like to know beforehand approximately how long
     11it takes to compile and install each package. Because Linux From
     12Scratch can be built on many different systems, it is impossible to
     13provide accurate time estimates.  The biggest package (Glibc) will
     14take approximately 20 minutes on the fastest systems, but could take
     15up to three days on slower systems! Instead of providing actual times,
     16the <emphasis>Static Binutils Unit</emphasis> (SBU) measure will be
     17used instead.</para>
    1818
    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>
     19<para>The SBU measure works like this?the first package to be compiled
     20from this book is the statically-linked Binutils in <xref
     21linkend="chapter-temporary-tools"/>.  The time it takes to compile
     22this package is what will be referred to as the Static Binutils Unit
     23or SBU. All other compile times will be expressed relative to this
     24time.</para>
    2425
    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>
     26<para>For example, consider a package whose compilation time is 4.5
     27SBUs. This means that if a system took 10 minutes to compile and
     28install the static Binutils, it will take
     29<emphasis>approximately</emphasis> 45 minutes to build this example
     30package. Fortunately, most build times are much shorter than the one
     31for Binutils.</para>
    3032
    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>
     33<para>Please note that if the system compiler on the host is GCC-2 based, the
     34SBUs listed may be somewhat understated. This is because the SBU is
     35based on the very first package, compiled with the old GCC, while the
     36rest of the system is compiled with the newer GCC-&gcc-version; (which is
     37known to be approximately 30 percent slower). SBUs are also not
     38highly accurate for SMP-based machines.</para>
    3639
    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
     40<para>To view actual timings for specific machines, we recommend
    4241<ulink url="&lfs-root;~bdubbs/"/>.</para>
    4342
     43<para>In general, SBUs are inaccurate because they depend on many
     44factors, not just the GCC version. The only reason they are provided
     45is to give some kind of indication of how long it might take to
     46install a package, but the numbers can be off by as much as dozens of
     47minutes in some cases.</para>
     48
    4449</sect1>
     50
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