On Wed, Nov 22, 2017 at 07:52:54AM +0100, Raffaele Belardi wrote: > Hi, > > rebuilding system and world with gcc-7.2.0 on a 6-core AMD CPU I have the > impression that > most of the ebuilds limit parallel builds to 1, 2 or 3 threads. I'm aware it > is only an > impression, I did not spend the night monitoring the process, but > nevertheless every time > I checked the load was very low.
multi-core is definitely worth it. Any non-trivial package (wine,glibc,gcc,llvm,qt off the top of my head) will spend a long time building many files that can be built in parallel with multiple make jobs. That being said: if you do a world rebuild you will have lots of packages that spend ~40 seconds doing their autoconf run, only to build 2-3 sources files. On an 8-core machine at work, I get good results using parallel emerge jobs (emerge -jX). For your 6-core AMD CPU (assuming it actually has 12 threads) I'd start with 'emerge -j3' and MAKEOPTS='-j12 -l16'. That should get you a nice speedup, but may require a bit more ram.
