Running "emerge -ev --buildpkg --keep-going @world" right now shows that portage only utilizes one CPU core when creating the binpackages. From what I see in the process list it seems portage is doing something similar like tar -cf ... | bzip2 which of course results in the compression being single-threaded because app-arch/bzip2 is not SMP capable. I'd like to request the possibility to create binary packages with full utilization of as much CPU cores as possible when being on multicore systems. We already have two bzip2 compresors in the portage tree that have SMP support: app-arch/lbzip2 app-arch/pbzip2
Turns out I'm just too stupid to read man pages. mgorny told me about PORTAGE_BZIP2_COMMAND variable which indeed serves my needs.