documentation: BB_NUMBER_THREADS and PARALLEL_MAKE suggestions

Text that suggests setting the BB_NUMBER_THREADS and
PARALLEL_MAKE variables to speed build time has been updated to
suggest a setting of twice the number of host cores supported.

The 2x number came to light through a discussion on the project
mailing list initiated by Robert P. J. Day.

Reported-by: Robert P. J. Day
(From yocto-docs rev: 1846b41a595b7bd905ca828eaa04112d1533d7a1)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 5 insertions, 6 deletions

diff --git a/documentation/dev-manual/dev-manual-kernel-appendix.xml b/documentation/dev-manual/dev-manual-kernel-appendix.xml
index 7ac349b6e3..0f13344800 100644
--- a/documentation/dev-manual/dev-manual-kernel-appendix.xml
+++ b/documentation/dev-manual/dev-manual-kernel-appendix.xml
@@ -221,9 +221,9 @@
                     If your host development system supports multi-core and multi-thread capabilities,
                     you can uncomment these statements and set the variables to significantly shorten
                     the full build time.
-                    As a guideline, set <filename>BB_NUMBER_THREADS</filename> to twice the number 
-                    of cores your machine supports and set <filename>PARALLEL_MAKE</filename> to one and 
-                    a half times the number of cores your machine supports.
+                    As a guideline, set both <filename>BB_NUMBER_THREADS</filename> and 
+                    <filename>PARALLEL_MAKE</filename> to twice the number 
+                    of cores your machine supports.
                 </note>
                 </para>
                 <para>
@@ -390,9 +390,8 @@
                        build time if your host supports multi-core and multi-thread capabilities:
                        <filename>BB_NUMBER_THREADS</filename> and <filename>PARALLEL_MAKE</filename>.
                        If the host system has multiple cores then you can optimize build time 
-                       by setting <filename>BB_NUMBER_THREADS</filename> to twice the number of 
-                       cores and setting <filename>PARALLEL_MAKE</filename> to one and a half times the 
-                       number of cores.</para></listitem>
+                       by setting both these variables to twice the number of 
+                       cores.</para></listitem>
                    <listitem><para><emphasis>Identify Your <filename>meta-kernel-dev</filename>
                        Layer:</emphasis> The <filename>BBLAYERS</filename> variable in the 
                        <filename>bblayers.conf</filename> file found in the