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+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+
+Speeding Up a Build
+*******************
+
+Build time can be an issue. By default, the build system uses simple
+controls to try and maximize build efficiency. In general, the default
+settings for all the following variables result in the most efficient
+build times when dealing with single socket systems (i.e. a single CPU).
+If you have multiple CPUs, you might try increasing the default values
+to gain more speed. See the descriptions in the glossary for each
+variable for more information:
+
+-  :term:`BB_NUMBER_THREADS`:
+   The maximum number of threads BitBake simultaneously executes.
+
+-  :term:`BB_NUMBER_PARSE_THREADS`:
+   The number of threads BitBake uses during parsing.
+
+-  :term:`PARALLEL_MAKE`: Extra
+   options passed to the ``make`` command during the
+   :ref:`ref-tasks-compile` task in
+   order to specify parallel compilation on the local build host.
+
+-  :term:`PARALLEL_MAKEINST`:
+   Extra options passed to the ``make`` command during the
+   :ref:`ref-tasks-install` task in
+   order to specify parallel installation on the local build host.
+
+As mentioned, these variables all scale to the number of processor cores
+available on the build system. For single socket systems, 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.
+
+Additional factors that can affect build speed are:
+
+-  File system type: The file system type that the build is being
+   performed on can also influence performance. Using ``ext4`` is
+   recommended as compared to ``ext2`` and ``ext3`` due to ``ext4``
+   improved features such as extents.
+
+-  Disabling the updating of access time using ``noatime``: The
+   ``noatime`` mount option prevents the build system from updating file
+   and directory access times.
+
+-  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.
+
+-  Choosing the packaging backend: Of the available packaging backends,
+   IPK is the fastest. Additionally, selecting a singular packaging
+   backend also helps.
+
+-  Using ``tmpfs`` for :term:`TMPDIR`
+   as a temporary file system: While this can help speed up the build,
+   the benefits are limited due to the compiler using ``-pipe``. The
+   build system goes to some lengths to avoid ``sync()`` calls into the
+   file system on the principle that if there was a significant failure,
+   the :term:`Build Directory` contents could easily be rebuilt.
+
+-  Inheriting the :ref:`ref-classes-rm-work` 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
+   :term:`TMPDIR` 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.
+
+Aside from the previous list, you should keep some trade offs in mind
+that can help you speed up the build:
+
+-  Remove items from
+   :term:`DISTRO_FEATURES`
+   that you might not need.
+
+-  Exclude debug symbols and other debug information: If you do not need
+   these symbols and other debug information, disabling the ``*-dbg``
+   package generation can speed up the build. You can disable this
+   generation by setting the
+   :term:`INHIBIT_PACKAGE_DEBUG_SPLIT`
+   variable to "1".
+
+-  Disable static library generation for recipes derived from
+   ``autoconf`` or ``libtool``: Here is an example showing how to
+   disable static libraries and still provide an override to handle
+   exceptions::
+
+      STATICLIBCONF = "--disable-static"
+      STATICLIBCONF:sqlite3-native = ""
+      EXTRA_OECONF += "${STATICLIBCONF}"
+
+   .. note::
+
+      -  Some recipes need static libraries in order to work correctly
+         (e.g. ``pseudo-native`` needs ``sqlite3-native``). Overrides,
+         as in the previous example, account for these kinds of
+         exceptions.
+
+      -  Some packages have packaging code that assumes the presence of
+         the static libraries. If so, you might need to exclude them as
+         well.
+