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SubjectRe: [PATCH 3/4] kbuild: create object directories simpler and faster
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Hi Masahiro-san,

On 11/09/2017 11:41 PM, Masahiro Yamada wrote:
> 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 resulted
> obj-dirs is as many "./" as objects.
>
> For those 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 bad code in arch/x86/entry/vdso/Makefile. This is now
> really unnecessary.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
> arch/x86/entry/vdso/Makefile | 4 ----
> scripts/Makefile.build | 15 ++++++---------
> scripts/Makefile.host | 11 -----------
> scripts/Makefile.lib | 5 -----
> 4 files changed, 6 insertions(+), 29 deletions(-)
>
> 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 @@ $(obj)/vdsox32.so.dbg: $(src)/vdsox32.lds $(vobjx32s) FORCE
> 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)) $(obj)/vdso32/
> -
> targets += vdso32/vdso32.lds
> targets += vdso32/note.o vdso32/system_call.o vdso32/sigreturn.o
> targets += vdso32/vclock_gettime.o
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 62d5314..89ac180 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -64,15 +64,6 @@ ifneq ($(hostprogs-y)$(hostprogs-m)$(hostlibs-y)$(hostlibs-m)$(hostcxxlibs-y)$(h
> include scripts/Makefile.host
> endif
>
> -ifneq ($(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
> $(warning kbuild: Makefile.build is included improperly)
> endif
> @@ -589,6 +580,12 @@ ifneq ($(cmd_files),)
> include $(cmd_files)
> endif
>
> +ifneq ($(KBUILD_SRC),)
> +# Create directories for object files if directory does not exist
> +obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
> +$(shell mkdir -p $(obj-dirs))
> +endif
> +

I just take a quick glance: is "$(obj)" here necessary? I think all
$(targets) are under directory $(obj) when we descend into $(obj) to
recursive make, if I don't miss anything.

--
Sincerely,
Cao jin

> # 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..3a5460d 100644
> --- a/scripts/Makefile.host
> +++ b/scripts/Makefile.host
> @@ -48,15 +48,6 @@ host-cxxobjs := $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
> 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))
> @@ -68,8 +59,6 @@ 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 @@ single-used-m := $(sort $(filter-out $(multi-used-m),$(obj-m)))
> # 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-used-m := $(addprefix $(obj)/,$(multi-used-m))
> 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
>



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