Oversubscription during build

[maleadt]

I noticed on amdci4 that all build jobs run with -j128 (the number of cores), significantly oversubscribing the machine (at the point I was logged in, making it very unresponsive to administer):

This should probably be capped to the number of cores assigned to the worker, if we do that?

[IanButterworth]

The new grafana buildkite dashboard shows that a lot platforms have build times with higher than expected variance.. I guess this contributes to that

Thanks to @fredrikekre for adding that

[fredrikekre]

The builder-* agents don't limit the number of cores but the tester-ones do.

[giordano]

The new grafana buildkite dashboard

How to get that?