build parallelism broken

[branfosj]

My default setup is to build in a Slurm interactive job with 8 cores allocated - so I'll be in a cgroup.

With EB 4.9.4 I correctly see make -j 8, but with EB 5 I am seeing make -j 16.

If I revert the changes to

• easybuild/framework/easyconfig/default.py
• easybuild/tools/options.py

from #4777 then I see the old behavior.

[branfosj]

In set_parallel() https://github.com/easybuilders/easybuild-framework/blob/5.0.x/easybuild/framework/easyblock.py#L2434

par = build_option('parallel')

will be 16 by default.

So in det_parallelism() https://github.com/easybuilders/easybuild-framework/blob/5.0.x/easybuild/tools/systemtools.py#L1211 par is always set and we bypass the code that detects the number of available cores.

[boegel]

Setting the limit to 16 via --parallel as was done in #4777 was wrong, we need a --max-parallel instead, implemented that in:

• add --max-parallel configuration option to control maximum number of cores to use, set to 16 by default #4816