[Buildroot] [PATCH v2] Makefile: add --no-builtin-rules flag
Yann E. MORIN
yann.morin.1998 at free.fr
Sat Mar 12 22:13:45 UTC 2016
Arnout, All,
On 2016-03-12 00:47 +0100, Arnout Vandecappelle (Essensium/Mind) spake thusly:
> When calling 'make', it takes several seconds before anything happens.
> This is because all the makefiles that have to be parsed and variables
> and rules that have to be evaluated.
>
> One of the rules to be evaluated are the implicit rules that make adds
> to check out the *.mk files from RCS etc. This obviously makes no
> sense. Therefore, disable the built-in rules.
>
> To avoid breaking package that depend on them, make sure we filter this
> out when calling sub-makes. MFLAGS has to be overridden too, otherwise
> the sub-make will just use that instead of MAKEFLAGS when MAKEFLAGS is
> empty.
>
> Time for 'make help > /dev/null' on my machine (with hot cache):
> before after
> real 0m4.167s 0m3.375s
> user 0m3.596s 0m2.928s
> sys 0m0.256s 0m0.180s
>
> and for 'make graph-depends' on a large config:
> before after
> real 0m58.417s 0m53.625s
> user 0m48.284s 0m43.680s
> sys 0m4.076s 0m3.536s
>
> A roughly 10% improvement.
>
> Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>
> ---
> v2: override MFLAGS as well.
> ---
> Makefile | 2 ++
> package/Makefile.in | 2 ++
> 2 files changed, 4 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index f2822a2..bbb2017 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -29,6 +29,8 @@ UMASK = 0022
> ifneq ($(shell umask),$(UMASK))
> .PHONY: _all $(MAKECMDGOALS)
>
> +%.mk:
> +
> $(MAKECMDGOALS): _all
> @:
>
> diff --git a/package/Makefile.in b/package/Makefile.in
> index fbf5485..730810e 100644
> --- a/package/Makefile.in
> +++ b/package/Makefile.in
> @@ -1,3 +1,4 @@
> +MAKEFLAGS += --no-builtin-rules
> ifndef MAKE
> MAKE := make
> endif
> @@ -5,6 +6,7 @@ ifndef HOSTMAKE
> HOSTMAKE = $(MAKE)
> endif
> HOSTMAKE := $(shell which $(HOSTMAKE) || type -p $(HOSTMAKE) || echo make)
> +HOSTMAKE += MAKEFLAGS="$(filter-out --no-builtin-rules,$(MAKEFLAGS))" MFLAGS=
Is the extra added complexity worth the improvement?
Regards,
Yann E. MORIN.
> # If BR2_JLEVEL is 0, scale the maximum concurrency with the number of
> # CPUs. An additional job is used in order to keep processors busy
> --
> 2.7.0
>
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