Changeset 86861ee for chapter04

Timestamp:

11/13/2009 02:09:23 AM (14 years ago)

Author:

Bruce Dubbs <bdubbs@…>

Branches:

10.0, 10.0-rc1, 10.1, 10.1-rc1, 11.0, 11.0-rc1, 11.0-rc2, 11.0-rc3, 11.1, 11.1-rc1, 11.2, 11.2-rc1, 11.3, 11.3-rc1, 12.0, 12.0-rc1, 12.1, 12.1-rc1, 6.6, 6.7, 6.8, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.5-systemd, 7.6, 7.6-systemd, 7.7, 7.7-systemd, 7.8, 7.8-systemd, 7.9, 7.9-systemd, 8.0, 8.1, 8.2, 8.3, 8.4, 9.0, 9.1, arm, bdubbs/gcc13, ml-11.0, multilib, renodr/libudev-from-systemd, s6-init, trunk, xry111/arm64, xry111/arm64-12.0, xry111/clfs-ng, xry111/lfs-next, xry111/loongarch, xry111/loongarch-12.0, xry111/loongarch-12.1, xry111/mips64el, xry111/pip3, xry111/rust-wip-20221008, xry111/update-glibc

Children:

10319487

Parents:

6ea017a2

Message:

Added a note to address parallel make procedures

git-svn-id: ​http://svn.linuxfromscratch.org/LFS/trunk/BOOK@9099 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

File:

• chapter04/aboutsbus.xml (modified) (1 diff)

chapter04/aboutsbus.xml

@@ -33 +33 @@
 
   <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>