lfs-book/chapter02/aboutsbus.xml

<sect1 id="ch02-aboutsbus">
<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>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 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>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>

</sect1>