Author: bdubbs
Date: 2009-11-12 19:09:23 -0700 (Thu, 12 Nov 2009)
New Revision: 9099
Modified:
trunk/BOOK/chapter01/changelog.xml
trunk/BOOK/chapter04/aboutsbus.xml
Log:
Added a note to address parallel make procedures
Modified: trunk/BOOK/chapter01/changelog.xml
===================================================================
--- trunk/BOOK/chapter01/changelog.xml 2009-11-12 16:52:28 UTC (rev 9098)
+++ trunk/BOOK/chapter01/changelog.xml 2009-11-13 02:09:23 UTC (rev 9099)
@@ -41,6 +41,11 @@
<para>2009-11-12</para>
<itemizedlist>
<listitem>
+ <para>[bdubbs] Added a note to 'About SBUs' to address
+ parallel make procedures and how SBU values will be
+ affected.</para>
+ </listitem>
+ <listitem>
<para>[bdubbs] Minor changes to GRUB-1.9.1 instructions.</para>
</listitem>
</itemizedlist>
Modified: trunk/BOOK/chapter04/aboutsbus.xml
===================================================================
--- trunk/BOOK/chapter04/aboutsbus.xml 2009-11-12 16:52:28 UTC (rev 9098)
+++ trunk/BOOK/chapter04/aboutsbus.xml 2009-11-13 02:09:23 UTC (rev 9099)
@@ -32,14 +32,33 @@
Fortunately, most build times are shorter than the one for Binutils.</para>
<para>In general, SBUs are not entirely accurate because they depend on many
- factors, including the host system's version of GCC. Note that on Symmetric
- Multi-Processor (SMP)-based machines, SBUs are even less accurate. They are
- provided here to give an estimate of how long it might take to install a
- package, but the numbers can vary by as much as dozens of minutes in some
- cases.</para>
+ factors, including the host system's version of GCC. They are provided here
+ to give an estimate of how long it might take to install a package, but the
+ numbers can vary by as much as dozens of minutes in some cases.</para>
<para>To view actual timings for a number of specific machines, we recommend
The LinuxFromScratch SBU Home Page at <ulink url="&lfs-root;~sbu/"/>.</para>
+ <note><para>For many modern systems with multiple processors (or cores) the
+ compilation time for a package can be reduced by performing a "parallel make"
+ by either setting an environment variable or telling the
+ <command>make</command> program how many processors are available. For
+ instance, a Core2Duo can support two simultaneous processes with:</para>
+
+ <screen><userinput>set MAKEFLAGS='-j 2'</userinput></screen>
+
+ <para>or just building with:</para>
+
+ <screen><userinput>make -j2</userinput></screen>
+
+ <para>When multiple processors are used in this way, the SBU units in the
+ book will vary even more than they normally would. Analyzing the output of
+ the build process will also be more difficult because the lines of different
+ processes will be interleaved. If you run into a problem with a build step,
+ revert back to a single processor build to properly analyze the error
+ messages.</para>
+
+ </note>
+
</sect1>
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