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diff --git a/documentation/ref-manual/usingpoky.xml b/documentation/ref-manual/usingpoky.xml index 1a211ca78a..41f872c07e 100644 --- a/documentation/ref-manual/usingpoky.xml +++ b/documentation/ref-manual/usingpoky.xml @@ -888,6 +888,148 @@ </section> </section> +<section id='speeding-up-the-build'> + <title>Speeding Up the Build</title> + + <para> + Build time can be an issue. + By default, the build system uses three simple controls to try and + maximize build efficiency: + <itemizedlist> + <listitem><para> + <link linkend='var-BB_NUMBER_THREADS'><filename>BB_NUMBER_THREADS</filename></link> + </para></listitem> + <listitem><para> + <ulink url='&YOCTO_DOCS_BB_URL;#var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></ulink> + </para></listitem> + <listitem><para> + <link linkend='var-PARALLEL_MAKE'><filename>PARALLEL_MAKE</filename></link> + </para></listitem> + </itemizedlist> + These three variables all scale to the number of processor cores + available on the build system. + This auto-scaling ensures that the build system fundamentally takes + advantage of potential parallel operations during the build + based on the build machine's capabilities. + </para> + + <para> + If you need to achieve even faster builds than what the build system + produces by default, you can consider and implement some of the + following: + <itemizedlist> + <listitem><para> + <filename>BB_NUMBER_THREADS</filename>, + <filename>BB_NUMBER_PARSE_THREADS</filename>, and + <filename>PARALLEL_MAKE</filename>: + As previously mentioned, the build system scales the values + for these variables. + However, you can manually override them in your + <filename>local.conf</filename> file if you are not satisfied + with the defaults. + </para></listitem> + <listitem><para> + File system type: + The file system type that the build is being performed on can + also influence performance. + Using <filename>ext4</filename> is recommended as compared + to <filename>ext2</filename> and <filename>ext3</filename> + due to <filename>ext4</filename> improved features + such as extents. + </para></listitem> + <listitem><para> + Disabling the updating of access time using + <filename>noatime</filename>: + The <filename>noatime</filename> mount option prevents the + build system from updating file and directory access times. + </para></listitem> + <listitem><para> + Setting a longer commit: + Using the "commit=" mount option increases the interval + in seconds between disk cache writes. + Changing this interval from the five second default to + something longer increases the risk of data loss but decreases + the need to write to the disk, thus increasing the build + performance. + </para></listitem> + <listitem><para> + Choosing the packaging backend: + Of the available packaging backends, IPK is the fastest. + Additionally, selecting a singular packaging backend also + helps. + </para></listitem> + <listitem><para> + Using <filename>/tmp</filename> as a temporary file system: + While this can help speed up the build, the benefits are + limited due to the compiler using + <filename>-pipe</filename>. + The build system goes to some lengths to avoid + <filename>sync()</filename> calls into the + file system on the principle that if there was a significant + failure, the + <ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink> + contents could easily be rebuilt. + </para></listitem> + <listitem><para> + Inheriting the + <link linkend='ref-classes-rm-work'><filename>rm_work</filename></link> + class: + Inheriting this class has shown to speed up builds due to + significantly lower amounts of data stored in the data + cache as well as on disk. + Inheriting this class also makes cleanup of + <link linkend='var-TMPDIR'><filename>TMPDIR</filename></link> + faster, at the expense of being easily able to dive into the + source code. + File system maintainers have recommended that the fastest way + to clean up large numbers of files is to reformat partitions + rather than delete files due to the linear nature of partitions. + This, of course, assumes you structure the disk partitions and + file systems in a way that this is practical. + </para></listitem> + </itemizedlist> + Aside from the previous list, you should keep some trade offs in + mind that can help you speed up the build: + <itemizedlist> + <listitem><para> + Exclude debug symbols and other debug information: + If you do not need these symbols and other debug information, + disabling the <filename>*-dbg</filename> package generation + can speed up the build. + You can disable this generation by setting the + <link linkend='var-INHIBIT_PACKAGE_DEBUG_SPLIT'><filename>INHIBIT_PACKAGE_DEBUG_SPLIT</filename></link> + variable to "1". + </para></listitem> + <listitem><para> + Disable static library generation for recipes derived from + <filename>autoconf</filename> or <filename>libtool</filename>: + Following is an example showing how to disable static + libraries and still provide an override to handle exceptions: + <literallayout class='monospaced'> + STATICLIBCONF = "--disable-static" + STATICLIBCONF_sqlite3-native = "" + EXTRA_OECONF += "${STATICLIBCONF}" + </literallayout> + <note><title>Notes</title> + <itemizedlist> + <listitem><para> + Some recipes need static libraries in order to work + correctly (e.g. <filename>pseudo-native</filename> + needs <filename>sqlite3-native</filename>). + Overrides, as in the previous example, account for + these kinds of exceptions. + </para></listitem> + <listitem><para> + Some packages have packaging code that assumes the + presence of the static libraries. + If so, you might need to exclude them as well. + </para></listitem> + </itemizedlist> + </note> + </para></listitem> + </itemizedlist> + </para> +</section> </chapter> <!-- vim: expandtab tw=80 ts=4 |