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
8650c6298c (doc lint: make "lint-docs" non-.PHONY, 2021-10-15).

As seen in 4c64fb5aad (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>
This commit is contained in:
Ævar Arnfjörð Bjarmason 2022-03-03 17:04:19 +01:00 committed by Junio C Hamano
parent a9fda017f4
commit 0b6d0bc924
3 changed files with 27 additions and 27 deletions

View File

@ -434,25 +434,11 @@ quick-install-html: require-htmlrepo
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): .build/lint-docs/gitlink/%.ok: %.txt
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)

View File

@ -2745,7 +2745,8 @@ all:: $(MOFILES)
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 @@ NO_PERL_CPAN_FALLBACKS_SQ = $(subst ','\'',$(NO_PERL_CPAN_FALLBACKS))
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 @@ test_bindir_programs := $(patsubst %,bin-wrappers/%,$(BINDIR_PROGRAMS_NEED_X) $(
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)))|' < $< > $@ && \

View File

@ -53,6 +53,8 @@ ifndef V
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 @@ ifndef V
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