Upstreams has the opinion, that the ebuild should configure it :
Are they right ?
This comment summarizes the upstream link.
Toralf reports a problem:
> I configured "make -j5" at my stable Gentoo, but the process lists shows, that each of 2 perl jobs runs 5 make jobs.
Upstream explains configure options:
> Our old (recursive) build system uses two configure options to determine how many jobs can be run:
> * --with-num-cpus tells how many directories can be build at once (one dmake process for each of them)
> * --with-max-jobs tells how many jobs each dmake can run
Upstreams addresses the ebuild maintainer:
> It is the ebuild's task to supply appropriate values for the options based on system-specific settings (e.g., MAKEFLAGS=-j5).
I closed this bug multiple times already.
It will be causing this issue until 4.0 release (3.7) where we addressed it correctly.
If i would set the -jobs to 1 then half of your build would not be paralel in older releases at all.