From: Rafael Sadowski <rafael@sizeofvoid.org>
Subject: Re: cmake.port.mk: limit max number of autogen moc/uic processes
To: Jeremie Courreges-Anglas <jca@wxcvbn.org>
Cc: ports@openbsd.org, landry@openbsd.org
Date: Thu, 2 May 2024 18:05:28 +0200

On Wed May 01, 2024 at 08:54:44PM GMT, Jeremie Courreges-Anglas wrote:
> 
> Some projects use cmake_autogen to generate moc/uic/rcc jobs.  The max
> number of parallel jobs to run is AUTOGEN_PARALLEL[0], itself
> initialized by CMAKE_AUTOGEN_PARALLEL.  By default it's empty, which
> means cmake_autogen will start up to $ncpus jobs on the system.  Those
> $ncpus are children of the cmake_autogen process and aren't accounted
> in the global pool of ${MAKE_JOBS} jobs.  So if you build an affected
> port with MAKE_JOBS=1 on a 16 cores machine, you end up with 1
> cmake_autogen job + 16 moc/uic jobs = 17 jobs.  That's not nice as we
> may have other ports building in parallel.
> 
> The diff below attempts to limit the max number of autogen jobs to
> ${MAKE_JOBS}, so that the max number of jobs running at any time
> doesn't exceed 2 * ${MAKE_JOBS}.  Looks like there is no way to get
> exactly ${MAKE_JOBS} jobs in total, but hopefully the behavior should
> now be saner.
> 
> Issue spotted while looking at qgis.  Thoughts?  ok?
> 
> [0] https://cmake.org/cmake/help/latest/prop_tgt/AUTOGEN_PARALLEL.html
> [1] https://cmake.org/cmake/help/latest/variable/CMAKE_AUTOGEN_PARALLEL.html

I didn't know that we could also control this! Great finding!

Tested with digikam and it looks like "/usr/local/bin/cmake -E
cmake_autogen" uses the correct ${MAKE_JOBS} jobs.

> 
> 
> Index: cmake.port.mk
> ===================================================================
> RCS file: /home/cvs/ports/devel/cmake/cmake.port.mk,v
> diff -u -p -r1.84 cmake.port.mk
> --- cmake.port.mk	29 Jul 2023 11:53:23 -0000	1.84
> +++ cmake.port.mk	1 May 2024 18:49:32 -0000
> @@ -13,6 +13,10 @@ CONFIGURE_ENV += MODCMAKE_USE_SHARED_LIB
>  MAKE_ENV += MODCMAKE_USE_SHARED_LIBS=yes
>  .endif
>  
> +# Limit the number of moc/uic processes started by cmake_autogen
> +# (default: number of CPUs on the system)
> +CONFIGURE_ARGS += -DCMAKE_AUTOGEN_PARALLEL=${MAKE_JOBS}
> +
>  USE_NINJA ?= Yes
>  
>  .if ${USE_NINJA:L} == "yes"

Could we add it above, please?

"CONFIGURE_ARGS :=>-------DCMAKE_ADDR2LINE:FILEPATH=/usr/bin/addr2line"

Otherwise OK rsadowski