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SubjectRe: [PATCH 4/4] kbuild: optimize object directory creation for incremental build
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Masahiro-san

On 11/09/2017 11:41 PM, Masahiro Yamada wrote:
> The previous commit largely optimized the object directory creation.
> We can optimize it more for incremental build.
>
> There are already *.cmd files in the output directory. The existing
> *.cmd files have been picked up by $(wildcard ...). Obviously,
> directories containing them exist too, so we can skip "mkdir -p".
>
> With this, Kbuild runs almost zero "mkdir -p" in incremental building.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
> scripts/Makefile.build | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 89ac180..90ea7a5 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -583,8 +583,13 @@ endif
> ifneq ($(KBUILD_SRC),)
> # Create directories for object files if directory does not exist
> obj-dirs := $(sort $(obj) $(patsubst %/,%, $(dir $(targets))))
> +# If cmd_files exist, their directories apparently exist. Skip mkdir.
> +exist-dirs := $(sort $(patsubst %/,%, $(dir $(cmd_files))))
> +obj-dirs := $(strip $(filter-out . $(exist-dirs), $(obj-dirs)))

First I am not sure if the dot "." here is necessary, because I guess
kbuild always descend into subdir do recursive make, so, very
$(cmd_files) should have at least 1 level dir.

Second, Assuming that "." probably exists, would it be "./"? because it
is what "dir" function returns.

--
Sincerely,
Cao jin

> +ifneq ($(obj-dirs),)
> $(shell mkdir -p $(obj-dirs))
> endif
> +endif
>




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