Re: [gentoo-user] is multi-core really worth it?

[Jeremi Piotrowski <jeremi.piotrowski@gmail.com>]

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.