Get at the tinderbox this process tree :-/ : tinderbox@mr-fox ~ $ pstree -Ulnspu 6812 init(1)───sudo(6705)───bwrap.sh(6724)───bwrap(6812)───bwrap(6816)───entrypoint(6828)───entrypoint(31209)───emerge(31210)───python3.8(23568)───python3.8(23569)───sandbox(23577)───ebuild.sh(23578)───ebuild.sh(23596)─┬─tee(23620) └─python3.8(23647)─┬─{python3.8}(3485) ├─{python3.8}(3984) ├─{python3.8}(4193) ├─{python3.8}(4394) ├─{python3.8}(4526) ├─{python3.8}(4558) ├─{python3.8}(4608) ├─{python3.8}(4943) ├─{python3.8}(4950) ├─{python3.8}(4951) ├─{python3.8}(4955) ├─{python3.8}(4958) ├─python3.8(23789)───python3.8(4953) ├─python3.8(23790)───x86_64-pc-linux(4673)───collect2(4723)───ld(4808) ├─python3.8(23791) ├─python3.8(23792)───x86_64-pc-linux(4952)───collect2(4954) ├─python3.8(23793)───x86_64-pc-linux(4205)───collect2(4218)───ld(4233) ├─python3.8(23794)───x86_64-pc-linux(4539)───collect2(4581)───ld(4583) ├─python3.8(23795)───x86_64-pc-linux(4945)───collect2(4947)───ld(4949) ├─python3.8(23801) ├─python3.8(23802)───x86_64-pc-linux(3487)───collect2(3490)───ld(3491) ├─python3.8(23803)───x86_64-pc-linux(4400)───collect2(4415)───ld(4417) ├─python3.8(23804)───x86_64-pc-linux(3987)───collect2(4010)───ld(4013) ├─python3.8(23805)───x86_64-pc-linux(4560)───collect2(4606)───ld(4617) └─{python3.8}(24279) Nearly all other packages in themean while (except few Go packages maybe) do respect -j1