Bug#1026962: openjfx: tries to build with -j64 on a host with 2 processors

[tony mancill]

On Sat, Dec 24, 2022 at 05:25:40PM -0800, tony mancill wrote:
> On Sat, Dec 24, 2022 at 08:22:43PM +0100, Aurelien Jarno wrote:
> > Source: openjfx
> > Version: 11.0.11+0-1.1
> > Severity: serious
> > Tags: ftbfs
> > Justification: fails to build from source (but built successfully in the past)
> > 
> > openjfx tries to build with -j64 on zani.debian.org, which only has 2
> > processors and 8GB of RAM:
> > 
> > buildd   3853047  0.0  0.0  67668     4 ?        S    11:07   0:00 cmake --build /build/openjfx-fzmlCD/openjfx-11.0.11+1/modules/javafx.web/build/linux/Release --config Release -- -j64
> > buildd   3853048  0.0  0.0   3200   272 ?        S    11:07   0:00 /usr/bin/gmake -f Makefile -j64
> > 
> > This hogs the buildd resources and we had to kill the build.
> 
> Yeah, that seems excessive.  FWIW, the most recent upload didn't change
> anything related to the build options, so this has built successfully in
> the past.
> 
> It built successfully on armel with the auto-detected value -j4, so it's
> surprising to see it pick 64 if there are only 2 processors.  The only
> reference to the number of compile threads is this bit of Groovy from
> build.gradle:
> 
> defineProperty("NUM_COMPILE_THREADS", "${Runtime.runtime.availableProcessors()}")
> 
> I will have a look to try to determine where the value of 64 is coming
> from.  We can clamp the value if need be.

I have been poking at this and the issue isn't with NUM_COMPILE_THREADS.
It appears that cmake is picking the value of 64 all by itself, and it
doesn't respect CMAKE_BUILD_PARALLEL_LEVEL when it is set in the build
environment.  So perhaps cmake has changed.

In any event, I will continue to look for a way to avoid this on s390x.