since ARM64 builds are significantly slower than AMD64 builds,
this is actually one of things we observe - some builds are couple of seconds faster, some take significantly longer when comparing AMD vs ARM. We’re still gathering data on this, but it seems, with current capacity being available, it depends a lot on how the things are structured in code and tests. Still the 50 minute timeout cap change is indeed something that we’ll look into soon as a quick remedy.
since it offers 32 CPUs for a job, amd64 only offers 2
Every LXD container is assigned also with 2vCPU amount when starting up (see our CI Environments -> Overview documentation, however the LXD host can dynamically shuffle available CPU time for the jobs. There’s a nice top level explanation on LXD resource usage control by LXD lead dev, Stéphane Graber. Thus, computing resources assigned to build job can vary for each build triggered depending on current LXD host workload. So wrt
I don’t expect this to last past the alpha stage.
It all depends on utilization of ARM infrastructure. I’d expect there would be days or times of the day, where there’s a plenty of capacity free for your more complex builds (if you think in terms of nightly builds etc).
And yes, it’s good idea to optimize your workload for parallel processing if this fits your case.
Hope it helps and gives an insight on resources behind your ARM build job?