Parallel emerge versus parallel make
I’d like to provide a public, extended answer to a friend of mine who asked me earlier today why I’m not using Portage 2.2’s parallel emerge feature.
Well, first of all, parallel emerge is helpful on SMP system during a first install, a world rebuild (which is actually what I’m doing now) or in a long update after some time spent offline; it is of little help when doing daily upgrades, or when installing a new package.
The reason is that you can effectively only merge in parallel packages that are independent of each other. And this is not so easy to ensure, to avoid breaking stuff, I’m sure portage is taking the safe route and rather serialise instead of risking brokenness. But even this, expects the dependency tree to be complete. You won’t find it complete because packages building with GCC are not going to depend on it. The system package set is not going to be put in the DEPEND variables of each ebuilds, as it is, and this opens the proverbial vase to a huge amount of problems, in my view. (Now you can also look up an earlier proposal of mine, and see if it had sense then already).