kbuild: create directory for make cache only when necessary (9a234a2e) · Commits · 戴 / test

Currently, the existence of $(dir $(make-cache)) is always checked, and created if it is missing. We can avoid unnecessary system calls by some tricks. [1] If KBUILD_SRC is unset, we are building in the source tree. The output directory checks can be entirely skipped. [2] If at least one cache data is found, it means the cache file was included. Obviously its directory exists. Skip "mkdir -p". [3] If Makefile does not contain any call of __run-and-store, it will not create a cache file. No need to create its directory. [4] The "mkdir -p" should be only invoked by the first call of __run-and-store Signed-off-by:

Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by:

Douglas Anderson <dianders@chromium.org>

scripts/Kbuild.include

+9 −4

Original line number	Diff line number	Diff line
		@@ -99,18 +99,19 @@ cc-cross-prefix = \

		# Include values from last time
		make-cache := $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/,$(if $(obj),$(obj)/)).cache.mk
		ifeq ($(wildcard $(dir $(make-cache))),)
		$(shell mkdir -p '$(dir $(make-cache))')
		endif
		$(make-cache): ;
		-include $(make-cache)

		cached-data := $(filter __cached_%, $(.VARIABLES))

		# If cache exceeds 1000 lines, shrink it down to 500.
		ifneq ($(word 1000,$(filter __cached_%, $(.VARIABLES))),)
		ifneq ($(word 1000,$(cached-data)),)
		$(shell tail -n 500 $(make-cache) > $(make-cache).tmp; \
		mv $(make-cache).tmp $(make-cache))
		endif

		create-cache-dir := $(if $(KBUILD_SRC),$(if $(cache-data),,1))

		# Usage: $(call __sanitize-opt,Hello=Hola$(comma)Goodbye Adios)
		#
		# Convert all '$', ')', '(', '\', '=', ' ', ',', ':' to '_'
		@@ -136,6 +137,10 @@ __sanitize-opt = $(subst $$,_,$(subst $(right_paren),_,$(subst $(left_paren),_,$
		define __run-and-store
		ifeq ($(origin $(1)),undefined)
		$$(eval $(1) := $$(shell $$(2)))
		ifeq ($(create-cache-dir),1)
		$$(shell mkdir -p $(dir $(make-cache)))
		$$(eval create-cache-dir :=)
		endif
		$$(shell echo '$(1) := $$($(1))' >> $(make-cache))
		endif
		endef

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