Our new compute server builds Firefox Nightly from source in 4 minutes 22 seconds, as well it should given how beefy it is. The build process does manage to get the machine to 100% usage of all CPUs, which is impressive (and nice) since there are 112 of them.
Then in response to a question about the link phase's duration and parallelism :
The usage of all CPUs lasts about two minutes, with a ramp up at the start and down at the end, then some wiggly usage of a lot fewer CPUs, with a couple of periods where only three are being used (and up to 10-13 in use). I can't see a clear link phase in the build report.
(This is for a full from scratch build.)
This is a (very) big server but in some respects not an unusual one; subject to component availability (and money), anyone could get their own version relatively trivially. It has two AMD Epyc 7453 28-core processors (hence the odd number of CPUs), 512 GB of RAM, and two NVMe drives in a software RAID mirror.
(Or instead of buying one, you could probably rent time on an equivalent server from a cloud provider on a minute by minute basis.)
As officially reported in Ubuntu 18.04, the server has only two NUMA zones :
node distances: node 0 1 0: 10 32 1: 32 10
I'm not sure this is completely accurate for Zen 3 Epycs in practice, but it's the official view.
One interesting effect of the NVMe drives (and perhaps other things) is that a build with a cold disk cache for the Firefox Nightly source tree is only a few seconds slower than a build with a warm cache. However, the NVMe drives do slow down enough under load that despite Linux software RAID preferring to read from the first disk , it sometimes reads from the second drive, although nowhere as much. This has the interesting effect that the second NVMe drive reports a lower average IO time than the first one.
(All of this is captured with a certain degree of granularity through our Prometheus based metrics system .)
There was a day when a system like this would have been essentially impossible for us to have; something this big and powerful would have been far too expensive for us to afford (and also physically very large and probably required special power). I rather enjoy how the world has changed to bring more and more computational power into our hands.