1 files changed, 4 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 61e678bd9751..52f35d2facd7 100644
--- a/Makefile
+++ b/Makefile
@@ -185,7 +185,10 @@ buildworld: upgrade_checks
 # files with chflags set, so this unsets them and tries the 'rm' a
 # second time.  There are situations where this target will be cleaning
 # some directories via more than one method, but that duplication is
-# needed to correctly handle all the possible situations.
+# needed to correctly handle all the possible situations.  Removing all
+# files without the immutable flag set in the first 'rm' instance saves
+# time, because 'chflags' will need to operate on fewer files (with the
+# immutable flag set) afterwards.
 #
 BW_CANONICALOBJDIR:=${MAKEOBJDIRPREFIX}${.CURDIR}
 cleanworld: