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settingenviron: Set MAKEFLAGS for parallelism in ~lfs/.bashrc

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Xi Ruoyao 2023-09-11 14:42:06 +08:00
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2 changed files with 49 additions and 12 deletions
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12
chapter04/aboutsbus.xml
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@ -37,18 +37,6 @@
numbers can vary by as much as dozens of minutes in some cases.</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, an Intel i5-6500 CPU can support four simultaneous processes with:</para>
<screen role="nodump"><userinput>export MAKEFLAGS='-j4'</userinput></screen>
<para>or by building with:</para>
<screen role="nodump"><userinput>make -j4</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. In some cases, the make
step will simply fail. Analyzing the output of the build process will also

49
chapter04/settingenviron.xml
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@ -195,6 +195,55 @@ EOF</userinput></screen>
completed LFS system.</para>
</important>
<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 telling the make program how many processors are available via
a command line option or an environment variable. For instance, an Intel
Core i9-13900K processor has 8 P (performance) cores and
16 E (efficiency) cores, and a P core can simultaneously run two threads
so each P core are modeled as two logical cores by the Linux kernel.
As the result there are 32 logical cores in total. One obvious way to
use all these logical cores is allowing <command>make</command> to spawn
up to 32 build jobs. This can be done by passing the
<parameter>-j32</parameter> option to <command>make</command>:
</para>
<screen role='nodump'><userinput>make -j32</userinput></screen>
<para>
Or set the <envar>MAKEFLAGS</envar> environment variable and its
content will be automatically used by <command>make</command> as
command line options:
</para>
<screen role='nodump'><userinput>export MAKEFLAGS=-j32</userinput></screen>
<important>
<para>
Never pass a <parameter>-j</parameter> option without a number to
<command>make</command> or set such an option in
<envar>MAKEFLAGS</envar>. Doing so will allow <command>make</command>
to spawn infinite build jobs and cause system stability issue.
</para>
</important>
<para>
To use all logical cores available for building packages in
<xref linkend='chapter-cross-tools'/> and
<xref linkend='chapter-temporary-tools'/>, set <envar>MAKEFLAGS</envar>
now in <filename>.bashrc</filename>:
</para>
<screen><userinput>cat &gt;&gt; ~/.bashrc &lt;&lt; "EOF"
<literal>export MAKEFLAGS=-j<replaceable>$(nproc)</replaceable></literal>
EOF</userinput></screen>
<para>
Replace <replaceable>$(nproc)</replaceable> with the number of logical
cores you want to use if you don't want to use all the logical cores.
</para>
<para>Finally, to ensure the environment is fully prepared for building the
temporary tools, force the <command>bash</command> shell to read
the new user profile:</para>