[cfarm-users] Setting up GitLab CI for git.git on the farm

[Segher Boessenkool]

On Sun, Nov 25, 2018 at 01:14:31PM +0100, Stefan Ring via cfarm-users wrote:
> On Sun, Nov 25, 2018 at 10:25 AM Baptiste Jonglez via cfarm-users
> <cfarm-users at lists.tetaneutral.net> wrote:
> >
> > According to ansible [https://cfarm.tetaneutral.net/machines/list/] gcc112
> > has 160 cores, and gcc135 has 128 cores.  Is ansible getting this wrong?
> 
> 8 threads per core. It really does not make sense to target more than
> one job for each core. Things will just get horribly slow.

No, that's not true, up to 4 jobs per core still gives considerable
speedup (and 8 a little too, depends).  Performance _per thread_ is lower
of course, but aggregate is higher.  SMT4 gets about twice as much work
done as single-threaded (which means each thread gets about half as much
done, but the total doubles).  Very roughly, depends on what you are doing
exactly, etc.

lscpu gets it right on all these machines btw (110, 112, 135); what does
ansible use?


Segher