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diff --git a/chapter02/aboutsbus.xml b/chapter02/aboutsbus.xml index c6ad47071..bc99d206b 100644 --- a/chapter02/aboutsbus.xml +++ b/chapter02/aboutsbus.xml @@ -2,28 +2,29 @@ <title>About SBUs</title> <?dbhtml filename="aboutsbus.html" dir="chapter02"?> -<para>SBUs are <emphasis>Static Bash Units</emphasis> and they are our way -of identifying how long a package takes to compile. Why don't we use normal -times like anybody else?</para> +<para>Most people would like to know beforehand how long it approximately +takes to compile and install each package. But "Linux from Scratch" is built +on so many different systems, it is not possible to give actual times that are +anywhere near accurate: the biggest package (Glibc) won't take more than +twenty minutes on the fastest systems, but will take something like three days +on the slowest -- no kidding. So instead of giving actual times, we've come up +with the idea of using the <emphasis>Static Binutils Unit</emphasis> +(abbreviated to <emphasis>SBU</emphasis>).</para> -<para>The biggest problem is that times cannot be accurate, not even a -little bit. So many people install LFS on so many different systems, the -times it takes to compile something varies too much. One package may take -20 minutes on one system, but that same package may take 3 days on another -(this is not an exaggeration). So instead we've come up with a -<emphasis>Static Bash Unit</emphasis> or <emphasis>SBU</emphasis>.</para> +<para>It works like this: the first package you compile in this book is the +statically linked Binutils in Chapter 5, and the time it takes to compile this +package is what we call the "Static Binutils Unit" or "SBU". All other compile +times will be expressed relative to this time.</para> -<para>It works like this: the very first package you compile in this book -is Bash in Chapter 5 and it'll be statically linked. The time it takes to -compile this package will be the basis and called the SBU. All other -compile times are relative to the time it takes to install Bash. For -example, GCC-3.2 takes about 9.5 SBUs and it's proven that this number is -fairly consistent among a lot of different systems. So multiply 9.5 by the -number of seconds it takes for Bash to install (the SBU value) and you get -a close approximation of how long GCC will take on your system.</para> +<para>For example, the time it takes to build the static version of GCC is 3.9 +SBU. This means that if on your system it took 10 minutes to compile and +install the static Binutils, then you know it will take nearly 40 minutes to +build the static GCC. Fortunately, most build times are much shorter than the +one of Binutils.</para> -<para>Note: We've seen that SBUs don't work well on SMP based machines. So -all bets are off if you're lucky enough to have an SMP setup.</para> +<para>Note that SBUs don't work well for SMP-based machines. But if you're so +lucky as to have multiple processors, chances are that your system is so fast +that you don't mind.</para> </sect1> |