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@@ -914,43 +914,52 @@
914 914
915 <para> 915 <para>
916 Build time can be an issue. 916 Build time can be an issue.
917 By default, the build system uses three simple controls to try and 917 By default, the build system uses simple controls to try and maximize
918 maximize build efficiency: 918 build efficiency.
919 In general, the default settings for all the following variables
920 result in the most efficient build times when dealing with single
921 socket systems (i.e. a single CPU).
922 If you have multiple CPUs, you might try increasing the default
923 values to gain more speed.
924 See the descriptions in the glossary for each variable for more
925 information:
919 <itemizedlist> 926 <itemizedlist>
920 <listitem><para> 927 <listitem><para>
921 <link linkend='var-BB_NUMBER_THREADS'><filename>BB_NUMBER_THREADS</filename></link> 928 <link linkend='var-BB_NUMBER_THREADS'><filename>BB_NUMBER_THREADS</filename>:</link>
929 The maximum number of threads BitBake simultaneously executes.
922 </para></listitem> 930 </para></listitem>
923 <listitem><para> 931 <listitem><para>
924 <ulink url='&YOCTO_DOCS_BB_URL;#var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></ulink> 932 <ulink url='&YOCTO_DOCS_BB_URL;#var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename>:</ulink>
933 The number of threads BitBake uses during parsing.
925 </para></listitem> 934 </para></listitem>
926 <listitem><para> 935 <listitem><para>
927 <link linkend='var-PARALLEL_MAKE'><filename>PARALLEL_MAKE</filename></link> 936 <link linkend='var-PARALLEL_MAKE'><filename>PARALLEL_MAKE</filename>:</link>
937 Extra options passed to the <filename>make</filename> command
938 during the
939 <link linkend='ref-tasks-compile'><filename>do_compile</filename></link>
940 task in order to specify parallel compilation on the
941 local build host.
942 </para></listitem>
943 <listitem><para>
944 <link linkend='var-PARALLEL_MAKEINST'><filename>PARALLEL_MAKEINST</filename>:</link>
945 Extra options passed to the <filename>make</filename> command
946 during the
947 <link linkend='ref-tasks-install'><filename>do_install</filename></link>
948 task in order to specify parallel installation on the
949 local build host.
928 </para></listitem> 950 </para></listitem>
929 </itemizedlist> 951 </itemizedlist>
930 These three variables all scale to the number of processor cores 952 As mentioned, these variables all scale to the number of processor
931 available on the build system. 953 cores available on the build system.
932 This auto-scaling ensures that the build system fundamentally takes 954 For single socket systems, this auto-scaling ensures that the build
933 advantage of potential parallel operations during the build 955 system fundamentally takes advantage of potential parallel operations
934 based on the build machine's capabilities. 956 during the build based on the build machine's capabilities.
935 </para> 957 </para>
936 958
937 <para> 959 <para>
938 If you need to achieve even faster builds than what the build system 960 Following are additional factors that can affect build speed:
939 produces by default, you can consider and implement some of the
940 following:
941 <itemizedlist> 961 <itemizedlist>
942 <listitem><para> 962 <listitem><para>
943 <filename>BB_NUMBER_THREADS</filename>,
944 <filename>BB_NUMBER_PARSE_THREADS</filename>, and
945 <filename>PARALLEL_MAKE</filename>:
946 As previously mentioned, the build system scales the values
947 for these variables so you should probably not override
948 these to try to speed up a build.
949 However, for completeness regarding this list, it is worth
950 mentioning that you can manually override these variables
951 by setting them in your <filename>local.conf</filename> file.
952 </para></listitem>
953 <listitem><para>
954 File system type: 963 File system type:
955 The file system type that the build is being performed on can 964 The file system type that the build is being performed on can
956 also influence performance. 965 also influence performance.
@@ -981,7 +990,9 @@
981 helps. 990 helps.
982 </para></listitem> 991 </para></listitem>
983 <listitem><para> 992 <listitem><para>
984 Using <filename>/tmp</filename> as a temporary file system: 993 Using <filename>tmpfs</filename> for
994 <link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>
995 as a temporary file system:
985 While this can help speed up the build, the benefits are 996 While this can help speed up the build, the benefits are
986 limited due to the compiler using 997 limited due to the compiler using
987 <filename>-pipe</filename>. 998 <filename>-pipe</filename>.
@@ -1014,6 +1025,11 @@
1014 mind that can help you speed up the build: 1025 mind that can help you speed up the build:
1015 <itemizedlist> 1026 <itemizedlist>
1016 <listitem><para> 1027 <listitem><para>
1028 Remove items from
1029 <link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>
1030 that you might not need.
1031 </para></listitem>
1032 <listitem><para>
1017 Exclude debug symbols and other debug information: 1033 Exclude debug symbols and other debug information:
1018 If you do not need these symbols and other debug information, 1034 If you do not need these symbols and other debug information,
1019 disabling the <filename>*-dbg</filename> package generation 1035 disabling the <filename>*-dbg</filename> package generation