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-rw-r--r--doc/manual/opt-common.xml20
1 files changed, 19 insertions, 1 deletions
diff --git a/doc/manual/opt-common.xml b/doc/manual/opt-common.xml
index 3be9f5dd5..2d67162d7 100644
--- a/doc/manual/opt-common.xml
+++ b/doc/manual/opt-common.xml
@@ -98,7 +98,25 @@
linkend='conf-build-max-jobs'><literal>build-max-jobs</literal></link>
configuration setting, which itself defaults to
<literal>1</literal>. A higher value is useful on SMP systems or to
- exploit I/O latency. </para></listitem>
+ exploit I/O latency.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="opt-cores"><term><option>--cores</option></term>
+
+ <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It defaults to the value of the <link
+ linkend='conf-build-cores'><literal>build-cores</literal></link>
+ configuration setting, if set, or <literal>1</literal> otherwise.
+ The value <literal>0</literal> means that the builder should use all
+ available CPU cores in the system.</para></listitem>
</varlistentry>