Bug 83621

	/usr/src/UPDATING, although mentioning that disabling malloc debugging 
	flags will improve performance, doesn't give the method to do so.  
	Therefore, the question often comes up on the mailing lists.
	Additionally, UPDATING doesn't mention the relatively new 
	make cleanworld target.  (The handbook doesn't either.)

Fix: 

Err, google?--SH70jXfyqg2mvKHBgWN1AnqCx5zn4Rou2d6bGuRHP3ed6xp5
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--- UPDATING	Sun Jul 17 12:49:19 2005
+++ UPDATING.new	Sun Jul 17 12:59:12 2005
@@ -19,7 +19,8 @@
 	related kernel options, INVARIANTS, malloc debugging flags
 	in userland, and various verbose features in the kernel.  Many
 	developers choose to disable these features on build machines
-	to maximize performance.
+	to maximize performance.  (To disable malloc debugging, 
+	ln -s aj /etc/malloc.conf)
 
 20050711:
 	RELENG_6 branched here.
@@ -227,6 +228,10 @@
 	prefix all make commands with 'env -i '.  See the env(1) manual
 	page for more details.
 
+	As of FreeBSD-5.x there is now a make cleanworld target.  This
+	This removes the cruft of previous builds from /usr/obj.
+
+
 	To build a kernel
 	-----------------
 	If you are updating from a prior version of FreeBSD (even one just
@@ -264,6 +269,7 @@
 	# is listed here if you are upgrading from a really old current.
 
 	<make sure you have good level 0 dumps>
+	make cleanworld
 	make buildworld
 	make kernel KERNCONF=YOUR_KERNEL_HERE
 							[1]
@@ -301,6 +307,7 @@
 	To upgrade in-place from 5.x-stable to current
 	----------------------------------------------
 	<make sure you have good level 0 dumps>
+	make cleanworld
 	make buildworld					[9]
 	make kernel KERNCONF=YOUR_KERNEL_HERE		[8]
 							[1]