Changeset ac38e9dc for introduction/important
- Timestamp:
- 08/01/2015 04:26:22 AM (9 years ago)
- Branches:
- systemd-13485
- Children:
- ad6910d
- Parents:
- 4a83293
- File:
-
- 1 edited
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introduction/important/building-notes.xml
r4a83293 rac38e9dc 7 7 8 8 <sect1 id="unpacking"> 9 <?dbhtml filename=" unpacking.html"?>9 <?dbhtml filename="notes-on-building.html"?> 10 10 11 11 <sect1info> … … 133 133 <replaceable><command></replaceable> is returned as the result and not the 134 134 result of the <command>tee</command> command.</para> 135 136 </sect2> 137 138 <sect2 id="parallel-builds" xreflabel="Using Multiple Processors"> 139 <title>Using Multiple Processors</title> 140 141 <para>For many modern systems with multiple processors (or cores) the 142 compilation time for a package can be reduced by performing a "parallel 143 make" by either setting an environment variable or telling the make program 144 how many processors are available. For instance, a Core2Duo can support two 145 simultaneous processes with: </para> 146 147 <screen><userinput>export MAKEFLAGS='-j2'</userinput></screen> 148 149 <para>or just building with:</para> 150 151 <screen><userinput>make -j2</userinput></screen> 152 153 <para>Generally the number of processes should not exceed the number of 154 cores supported by the CPU. To list the processors on your 155 system, issue: <userinput>grep processor /proc/cpuinfo</userinput>. 156 </para> 157 158 <para>In some cases, using multiple processors may result in a 'race' 159 condition where the success of the build depends on the order of the 160 commands run by the <command>make</command> program. For instance, if an 161 execuatable needs File A and File B, attempting to link the program before 162 one of the dependent components is available will result in a failure. 163 This condition usually arises because the upstream developer has not 164 properly designated all the prerequsites needed to accomplish a step in the 165 Makefile.</para> 166 167 <para>If this occurs, the best way to proceed is to drop back to a 168 single processor build. Adding '-j1' to a make command will override 169 the similar setting in the MAKEFLAGS environment variable.</para> 135 170 136 171 </sect2>
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