I hesitate to ask how much memory was configured originally.
Certain subsystems within the buildworld build eat a huge amount of
memory. In particular, the GCC build within the buildworld has some
huge and complex files which eat a lot of memory while running and a
-j3 would potentially run three of those cc's simultaniously.
I remember doing buildworlds on very old machines... with 256M of ram
or less, and they would always bog down compiling gcc. Configuring a lot
of swap and not using any make parallelism got the build through those
files.
In modern day machines have enough memory that it's easy to forget about
build requirements, but we've seen people running VMs make the same
mistake of configuring too little memory. If you are going to be running
buildworlds I woulds say 512M is about the minimum that can be configured.
And you should always configure outsized swap space, like a gigabyte or
so, on VMs with low amounts of configured ram just so it can slog though
the memory intensive bits.
-Matt