kbuild: create object directories simpler and faster
For the out-of-tree build, scripts/Makefile.build creates output
directories, but this operation is not efficient.
scripts/Makefile.lib calculates obj-dirs as follows:
obj-dirs := $(dir $(multi-objs) $(obj-y))
Please notice $(sort ...) is not used here. Usually the result is
as many "./" as objects here.
For a lot of duplicated paths, the following command is invoked.
_dummy := $(foreach d,$(obj-dirs), $(shell [ -d $(d) ] || mkdir -p $(d)))
Then, the costly shell command is run over and over again.
I see many points for optimization:
[1] Use $(sort ...) to cut down duplicated paths before passing them
to system call
[2] Use single $(shell ...) instead of repeating it with $(foreach ...)
This will reduce forking.
[3] We can calculate obj-dirs more simply. Most of objects are already
accumulated in $(targets). So, $(dir $(targets)) is fine and more
comprehensive.
I also removed ugly code in arch/x86/entry/vdso/Makefile. This is now
really unnecessary.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index d540966..f8e3d85 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -129,10 +129,6 @@
CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds)
VDSO_LDFLAGS_vdso32.lds = -m32 -Wl,-m,elf_i386 -Wl,-soname=linux-gate.so.1
-# This makes sure the $(obj) subdirectory exists even though vdso32/
-# is not a kbuild sub-make subdirectory.
-override obj-dirs = $(dir $(obj)) $(obj)/vdso32/
-
targets += vdso32/vdso32.lds
targets += vdso32/note.o vdso32/system_call.o vdso32/sigreturn.o
targets += vdso32/vclock_gettime.o
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 6f60377..496ecd8 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -64,15 +64,6 @@
include scripts/Makefile.host
endif
-ifneq ($(KBUILD_SRC),)
-# Create output directory if not already present
-_dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
-
-# Create directories for object files if directory does not exist
-# Needed when obj-y := dir/file.o syntax is used
-_dummy := $(foreach d,$(obj-dirs), $(shell [ -d $(d) ] || mkdir -p $(d)))
-endif
-
ifndef obj
$(warning kbuild: Makefile.build is included improperly)
endif
@@ -589,6 +580,12 @@
include $(cmd_files)
endif
+ifneq ($(KBUILD_SRC),)
+# Create directories for object files if they do not exist
+obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
+$(shell mkdir -p $(obj-dirs))
+endif
+
# Declare the contents of the .PHONY variable as phony. We keep that
# information in a variable se we can use it in if_changed and friends.
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index 9cfd5c8..a5e0383 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -48,15 +48,6 @@
host-cshobjs := $(sort $(foreach m,$(host-cshlib),$($(m:.so=-objs))))
host-cxxshobjs := $(sort $(foreach m,$(host-cxxshlib),$($(m:.so=-objs))))
-# output directory for programs/.o files
-# hostprogs-y := tools/build may have been specified.
-# Retrieve also directory of .o files from prog-objs or prog-cxxobjs notation
-host-objdirs := $(dir $(__hostprogs) $(host-cobjs) $(host-cxxobjs))
-
-host-objdirs := $(strip $(sort $(filter-out ./,$(host-objdirs))))
-
-
-__hostprogs := $(addprefix $(obj)/,$(__hostprogs))
host-csingle := $(addprefix $(obj)/,$(host-csingle))
host-cmulti := $(addprefix $(obj)/,$(host-cmulti))
host-cobjs := $(addprefix $(obj)/,$(host-cobjs))
@@ -66,9 +57,6 @@
host-cxxshlib := $(addprefix $(obj)/,$(host-cxxshlib))
host-cshobjs := $(addprefix $(obj)/,$(host-cshobjs))
host-cxxshobjs := $(addprefix $(obj)/,$(host-cxxshobjs))
-host-objdirs := $(addprefix $(obj)/,$(host-objdirs))
-
-obj-dirs += $(host-objdirs)
#####
# Handle options to gcc. Support building with separate output directory
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 4d88ad7..5fbc46d 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -50,15 +50,11 @@
# objects depend on those (obviously)
multi-objs-y := $(foreach m, $(multi-used-y), $($(m:.o=-objs)) $($(m:.o=-y)))
multi-objs-m := $(foreach m, $(multi-used-m), $($(m:.o=-objs)) $($(m:.o=-y)))
-multi-objs := $(multi-objs-y) $(multi-objs-m)
# $(subdir-obj-y) is the list of objects in $(obj-y) which uses dir/ to
# tell kbuild to descend
subdir-obj-y := $(filter %/built-in.o, $(obj-y))
-# $(obj-dirs) is a list of directories that contain object files
-obj-dirs := $(dir $(multi-objs) $(obj-y))
-
# Replace multi-part objects by their individual parts, look at local dir only
real-objs-y := $(foreach m, $(filter-out $(subdir-obj-y), $(obj-y)), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))),$($(m:.o=-objs)) $($(m:.o=-y)),$(m))) $(extra-y)
real-objs-m := $(foreach m, $(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y)) $($(m:.o=-m))),$($(m:.o=-objs)) $($(m:.o=-y)) $($(m:.o=-m)),$(m)))
@@ -81,7 +77,6 @@
multi-objs-y := $(addprefix $(obj)/,$(multi-objs-y))
multi-objs-m := $(addprefix $(obj)/,$(multi-objs-m))
subdir-ym := $(addprefix $(obj)/,$(subdir-ym))
-obj-dirs := $(addprefix $(obj)/,$(obj-dirs))
# These flags are needed for modversions and compiling, so we define them here
# $(modname_flags) defines KBUILD_MODNAME as the name of the module it will