Allow and make effective -j option in "make web"

[lilypond.git] / Documentation / user / install.itely

diff --git a/Documentation/user/install.itely b/Documentation/user/install.itely
index e203291674081bfc183cb2239b5b3810c238eab4..cb16e07e057a5d364cfc952ea06aa87036c5be6a 100644 (file)
--- a/Documentation/user/install.itely
+++ b/Documentation/user/install.itely
@@ -359,17 +359,25 @@ less verbose build output, just like for building the programs.
 
 @knownissues
 
-@code{-j} command-line option of @command{make} is unsupported for
-building the documentation.  As the most time consuming task is
-running LilyPond to build images of music, the makefile variable
-@code{CPU_COUNT} may be set in @file{local.make} or on the command line
-to the number of @code{.ly} files that LilyPond should process
-simultaneously, e.g. on a bi-processor or dual core machine
+The most time consuming task for building the documentation is running
+LilyPond to build images of music, and there cannot be several
+simultaneously running @command{lilypond-book} instances, so @code{-j}
+@command{make} option does not significantly speed up the build process.
+To help speed it up, the makefile variable @var{CPU_COUNT} may be set
+in @file{local.make} or on the command line to the number of
+@code{.ly} files that LilyPond should process simultaneously, e.g. on
+a bi-processor or dual core machine
 
 @example
-make CPU_COUNT=2 web
+make -j3 CPU_COUNT=3 web
 @end example
 
+@noindent
+The recommended value of @var{CPU_COUNT} is one plus the number of
+cores or processors, but it is advisable to set it to a smaller value
+if your system has not enough RAM to run that many simultaneous
+LilyPond instances.
+
 If source files have changed since last documentation build, output
 files that need to be rebuilt are normally rebuilt, even if you do not
 run @code{make web-clean} first.  However, building dependencies in the