On Sun, Nov 25, 2018 at 10:23:41AM +0100, Baptiste Jonglez wrote: > On 24-11-18, Segher Boessenkool via cfarm-users wrote: > > On Sat, Nov 24, 2018 at 11:28:58PM +0100, Ævar Arnfjörð Bjarmason via > > cfarm-users wrote: > > > I've tried to be conservative about resources. It's all nice -n 19'd, > > > and with a conservative -j value relative to the number of cores: > > > https://gitlab.com/git-vcs/git-gitlab-ci/blob/b8d4645891aa/ci/gitlab/run-on-gcc-farm.sh#L62-163 > > > > At least for the Power machines, that isn't conservative at all. > > -j1 is conservative. -j24 is not conservative on a machine with 20 CPUs > > (gcc112), or 32 CPUs (gcc135). The AIX (gcc119) jobs seem to run for over > > an hour on half the machine? That's no good :-( > > According to ansible [https://cfarm.tetaneutral.net/machines/list/] gcc112 > has 160 cores, and gcc135 has 128 cores. Is ansible getting this wrong?
Yes. gcc110 is a Power7 with 16 cores, 64 threads. gcc112 is a Power8 with 20 cores, 160 threads. gcc135 is a Power9 with 32 cores, 128 threads. (Running more than 4 threads per core on a Power8 does not really help, so you can count gcc112 as 80 threads). Running many tasks using SMT hurts tasks that want to run single-threaded, of course. Linux is quite good at distributing things nicely, but oversubscription hurts. Automated tasks on shared systems should try to stay out of the way. Segher _______________________________________________ cfarm-users mailing list cfarm-users@lists.tetaneutral.net https://lists.tetaneutral.net/listinfo/cfarm-users
