Makefiles: add and use wildcard "mkdir -p" template
Add a template to do the "mkdir -p" of $(@D) (the parent dir of $@)
for us, and use it for the "make lint-docs" targets I added in
8650c6298c1 (doc lint: make "lint-docs" non-.PHONY, 2021-10-15).
As seen in 4c64fb5aad9 (Documentation/Makefile: fix lint-docs mkdir
dependency, 2021-10-26) maintaining these manual lists of parent
directory dependencies is fragile, in addition to being obviously
verbose.
I used this pattern at the time because I couldn't find another method
than "order-only" prerequisites to avoid doing a "mkdir -p $(@D)" for
every file being created, which as noted in [1] would be significantly
slower.
But as it turns out we can use this neat trick of only doing a "mkdir
-p" if the $(wildcard) macro tells us the path doesn't exist. A re-run
of a performance test similar to that noted downthread of [1] in [2]
shows that this is faster, in addition to being less verbose and more
reliable (this uses my "git-hyperfine" thin wrapper for "hyperfine"[3]):
$ git -c hyperfine.hook.setup= hyperfine -L rev HEAD~1,HEAD~0 -s 'make -C Documentation lint-docs' -p 'rm -rf Documentation/.build' 'make -C Documentation -j1 lint-docs'
Benchmark 1: make -C Documentation -j1 lint-docs' in 'HEAD~1
Time (mean ± σ): 2.914 s ± 0.062 s [User: 2.449 s, System: 0.489 s]
Range (min … max): 2.834 s … 3.020 s 10 runs
Benchmark 2: make -C Documentation -j1 lint-docs' in 'HEAD~0
Time (mean ± σ): 2.315 s ± 0.062 s [User: 1.950 s, System: 0.386 s]
Range (min … max): 2.229 s … 2.397 s 10 runs
Summary
'make -C Documentation -j1 lint-docs' in 'HEAD~0' ran
1.26 ± 0.04 times faster than 'make -C Documentation -j1 lint-docs' in 'HEAD~1'
So let's use that pattern both for the "lint-docs" target, and a few
miscellaneous other targets.
This method of creating parent directories is explicitly racy in that
we don't know if we're going to say always create a "foo" followed by
a "foo/bar" under parallelism, or skip the "foo" because we created
"foo/bar" first. In this case it doesn't matter for anything except
that we aren't guaranteed to get the same number of rules firing when
running make in parallel.
1. https://lore.kernel.org/git/211028.861r45y3pt.gmgdl@evledraar.gmail.com/
2. https://lore.kernel.org/git/211028.86o879vvtp.gmgdl@evledraar.gmail.com/
3. https://gitlab.com/avar/git-hyperfine/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/Makefile b/Documentation/Makefile
index 0f4ebded..1eb9192 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -434,25 +434,11 @@
print-man1:
@for i in $(MAN1_TXT); do echo $$i; done
-## Lint: Common
-.build:
- $(QUIET)mkdir $@
-.build/lint-docs: | .build
- $(QUIET)mkdir $@
-
## Lint: gitlink
-.build/lint-docs/gitlink: | .build/lint-docs
- $(QUIET)mkdir $@
-.build/lint-docs/gitlink/howto: | .build/lint-docs/gitlink
- $(QUIET)mkdir $@
-.build/lint-docs/gitlink/config: | .build/lint-docs/gitlink
- $(QUIET)mkdir $@
LINT_DOCS_GITLINK = $(patsubst %.txt,.build/lint-docs/gitlink/%.ok,$(HOWTO_TXT) $(DOC_DEP_TXT))
-$(LINT_DOCS_GITLINK): | .build/lint-docs/gitlink
-$(LINT_DOCS_GITLINK): | .build/lint-docs/gitlink/howto
-$(LINT_DOCS_GITLINK): | .build/lint-docs/gitlink/config
$(LINT_DOCS_GITLINK): lint-gitlink.perl
$(LINT_DOCS_GITLINK): .build/lint-docs/gitlink/%.ok: %.txt
+ $(call mkdir_p_parent_template)
$(QUIET_LINT_GITLINK)$(PERL_PATH) lint-gitlink.perl \
$< \
$(HOWTO_TXT) $(DOC_DEP_TXT) \
@@ -463,23 +449,18 @@
lint-docs-gitlink: $(LINT_DOCS_GITLINK)
## Lint: man-end-blurb
-.build/lint-docs/man-end-blurb: | .build/lint-docs
- $(QUIET)mkdir $@
LINT_DOCS_MAN_END_BLURB = $(patsubst %.txt,.build/lint-docs/man-end-blurb/%.ok,$(MAN_TXT))
-$(LINT_DOCS_MAN_END_BLURB): | .build/lint-docs/man-end-blurb
$(LINT_DOCS_MAN_END_BLURB): lint-man-end-blurb.perl
$(LINT_DOCS_MAN_END_BLURB): .build/lint-docs/man-end-blurb/%.ok: %.txt
+ $(call mkdir_p_parent_template)
$(QUIET_LINT_MANEND)$(PERL_PATH) lint-man-end-blurb.perl $< >$@
.PHONY: lint-docs-man-end-blurb
-lint-docs-man-end-blurb: $(LINT_DOCS_MAN_END_BLURB)
## Lint: man-section-order
-.build/lint-docs/man-section-order: | .build/lint-docs
- $(QUIET)mkdir $@
LINT_DOCS_MAN_SECTION_ORDER = $(patsubst %.txt,.build/lint-docs/man-section-order/%.ok,$(MAN_TXT))
-$(LINT_DOCS_MAN_SECTION_ORDER): | .build/lint-docs/man-section-order
$(LINT_DOCS_MAN_SECTION_ORDER): lint-man-section-order.perl
$(LINT_DOCS_MAN_SECTION_ORDER): .build/lint-docs/man-section-order/%.ok: %.txt
+ $(call mkdir_p_parent_template)
$(QUIET_LINT_MANSEC)$(PERL_PATH) lint-man-section-order.perl $< >$@
.PHONY: lint-docs-man-section-order
lint-docs-man-section-order: $(LINT_DOCS_MAN_SECTION_ORDER)
diff --git a/Makefile b/Makefile
index d4c0f4c..12f0841 100644
--- a/Makefile
+++ b/Makefile
@@ -2745,7 +2745,8 @@
endif
po/build/locale/%/LC_MESSAGES/git.mo: po/%.po
- $(QUIET_MSGFMT)mkdir -p $(dir $@) && $(MSGFMT) -o $@ $<
+ $(call mkdir_p_parent_template)
+ $(QUIET_MSGFMT)$(MSGFMT) -o $@ $<
LIB_PERL := $(wildcard perl/Git.pm perl/Git/*.pm perl/Git/*/*.pm perl/Git/*/*/*.pm)
LIB_PERL_GEN := $(patsubst perl/%.pm,perl/build/lib/%.pm,$(LIB_PERL))
@@ -2761,15 +2762,16 @@
endif
perl/build/lib/%.pm: perl/%.pm GIT-PERL-DEFINES
- $(QUIET_GEN)mkdir -p $(dir $@) && \
+ $(call mkdir_p_parent_template)
+ $(QUIET_GEN) \
sed -e 's|@@LOCALEDIR@@|$(perl_localedir_SQ)|g' \
-e 's|@@NO_GETTEXT@@|$(NO_GETTEXT_SQ)|g' \
-e 's|@@NO_PERL_CPAN_FALLBACKS@@|$(NO_PERL_CPAN_FALLBACKS_SQ)|g' \
< $< > $@
perl/build/man/man3/Git.3pm: perl/Git.pm
- $(QUIET_GEN)mkdir -p $(dir $@) && \
- pod2man $< $@
+ $(call mkdir_p_parent_template)
+ $(QUIET_GEN)pod2man $< $@
$(ETAGS_TARGET): $(FOUND_SOURCE_FILES)
$(QUIET_GEN)$(RM) $@+ && \
@@ -2903,7 +2905,7 @@
all:: $(TEST_PROGRAMS) $(test_bindir_programs)
bin-wrappers/%: wrap-for-bin.sh
- @mkdir -p bin-wrappers
+ $(call mkdir_p_parent_template)
$(QUIET_GEN)sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
-e 's|@@BUILD_DIR@@|$(shell pwd)|' \
-e 's|@@PROG@@|$(patsubst test-%,t/helper/test-%$(X),$(@F))$(patsubst git%,$(X),$(filter $(@F),$(BINDIR_PROGRAMS_NEED_X)))|' < $< > $@ && \
diff --git a/shared.mak b/shared.mak
index c45b281..4e1b62e 100644
--- a/shared.mak
+++ b/shared.mak
@@ -53,6 +53,8 @@
QUIET = @
QUIET_GEN = @echo ' ' GEN $@;
+ QUIET_MKDIR_P_PARENT = @echo $(wspfx_SQ) MKDIR -p $(@D);
+
## Used in "Makefile"
QUIET_CC = @echo ' ' CC $@;
QUIET_AR = @echo ' ' AR $@;
@@ -84,3 +86,18 @@
export V
endif
endif
+
+### Templates
+
+## mkdir_p_parent: lazily "mkdir -p" the path needed for a $@
+## file. Uses $(wildcard) to avoid the "mkdir -p" if it's not
+## needed.
+##
+## Is racy, but in a good way; we might redundantly (and safely)
+## "mkdir -p" when running in parallel, but won't need to exhaustively create
+## individual rules for "a" -> "prefix" -> "dir" -> "file" if given a
+## "a/prefix/dir/file". This can instead be inserted at the start of
+## the "a/prefix/dir/file" rule.
+define mkdir_p_parent_template
+$(if $(wildcard $(@D)),,$(QUIET_MKDIR_P_PARENT)$(shell mkdir -p $(@D)))
+endef
