Teach people about hw.memtest.tests.

Submitted by:	Allan Jude <freebsd@allanjude.com>

en_US.ISO8859-1/books/faq/book.xml

@@ -3669,6 +3669,26 @@ C:\="DOS"</programlisting>
 	    in &man.tunefs.8;.</para>
 	</answer>
       </qandaentry>
+
+      <qandaentry>
+	<question xml:id="slow-boot-memtest">
+	  <para>Why does &os; pause for a long time at boot when the
+	    system has large amounts of ram?</para>
+	</question>
+
+	<answer>
+	  <para>&os; does a short memory test early in the boot
+	    process.  This test usually only takes several seconds,
+	    however if the system has many 10s or 100s of gigabytes
+	    of memory it can take up to a few minutes.  This test
+	    can be disabled by setting the
+	    <literal>hw.memtest.tests</literal> to
+	    <literal>0</literal> in
+	    <filename>/boot/loader.conf</filename>.</para>
+
+	  <para>For more details, see &man.loader.conf.5;.</para>
+	</answer>
+      </qandaentry>
     </qandaset>
 
     <sect1 xml:id="all-about-zfs">