From owner-freebsd-audit  Sun Feb 11  8:30:58 2001
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To: audit@freebsd.org, peter@freebsd.org, bde@freebsd.org
Subject: kmod.mk patches to fix excessive recompiling
Date: Sun, 11 Feb 2001 09:30:53 -0700
From: Warner Losh <imp@harmony.village.org>
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For a long time I've noticed that too many things recompile in the
modules when I rebuild after a cvs update.  I've tracked the problem
down now.

kmod.mk puts @ and machine as dependencies for all the sources.  This
is done to ensure that the link exists, but for no other reasons.
However, when the link does exist, the directory mod time comes into
consideration (that directory is the target of the symlink).  So,
whenever $S or $S/$MACHINE/include changes, all files are rebuilt inn
the modules tree.  My laptop is only a 300MHz Pentium, so this can
take longer than my attention span.

Please find enclosed patches that fix this problem.  They just add
checks to see if the files don't exist before making them a
dependency.  This works well for me and so I'm sharing it with the
world.

The prime motivator to finding this problem was vi dumped core in
src/sys and that caused all the modules to recompile.  Needless to
say, this ticked me off enough to fix this problem (but strangely, not
enough to upgrade my laptop's userland to fix vi :-).

Warner



Index: kmod.mk
===================================================================
RCS file: /home/imp/FreeBSD/CVS/src/sys/conf/kmod.mk,v
retrieving revision 1.90
diff -u -r1.90 kmod.mk
--- kmod.mk	2001/01/28 21:24:05	1.90
+++ kmod.mk	2001/02/11 16:25:20
@@ -158,7 +158,14 @@
 .MAIN: all
 all: objwarn ${PROG} all-man _SUBDIR
 
-beforedepend ${OBJS}: ${_ILINKS}
+beforedepend ${OBJS}:
+.if !exists(@)
+beforedepend ${OBJS}: @
+.endif
+.if !exists(machine)
+beforedepend ${OBJS}: machine
+.endif
+
 
 # Search for kernel source tree in standard places.
 .for _dir in ${.CURDIR}/../.. ${.CURDIR}/../../.. /sys /usr/src/sys
@@ -269,7 +276,9 @@
 .for _src in ${SRCS:M${_srcsrc:T:R}.${_ext}}
 CLEANFILES+=	${_src}
 .if !target(${_src})
+.if !exists(@)
 ${_src}: @
+.endif
 .if exists(@)
 ${_src}: @/kern/makeobjops.pl @/${_srcsrc}
 .endif
@@ -282,7 +291,9 @@
 .for _ext in c h
 .if ${SRCS:Mvnode_if.${_ext}} != ""
 CLEANFILES+=	vnode_if.${_ext}
+.if !exists(@)
 vnode_if.${_ext}: @
+.endif
 .if exists(@)
 vnode_if.${_ext}: @/kern/vnode_if.pl @/kern/vnode_if.src
 .endif


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