My build machine has 8 cores + HT so bitbake enthusiastically assumes
16. However I have (only?) 16GB of RAM (+24GB swap space).

16GB of RAM has always been more then enough with 4 core + HT, but now
building certain recipes (nodejs, but rust will probably do it as well)
eats up more memory then there actually is RAM causing excessive swapping.

In fact the swapping is so excessive that just this single recipe
determines largely the total image build time. However restricting
bitbake (or actually parallel make) to use only 4 cores + HT sounds also
like a waste.

I know this has been looked at in the past, but I think it needs
fundamental resolving (other then, hé, why not add just another stick of
memory).

What I do manually when I run into swapping so bad my desktop becomes
unresponsive is ssh from another machine and then stop (not kill) the
processes that use the most memory.

These then get swapped out, but not back in, allowing the remaining
tasks to complete without swapping. Then when sufficient memory becomes
free again I continue the stopped processes.

Isn't this something that could be added to bitbake to automate using
memory efficiently?