Mathias and I where discussing some challenges around fitting the Ceph build with any level of parallelism in to a virtualized launchpad builder (as used for the majority of architectures today).
Basically the current memory spec only permits a max-parallel of 2 (on Xenial amd64). Ceph is a big C++ project so takes some time to build with such a low level of parallelism.
Would it be possible to nudge up the default memory allocation on the builders? I use a 16G machine for test builds of i386/amd64 and I've not seen any memory exhaustion with parallel=8.
Or maybe have a mechanism to allow a source package to request a higher spec of builder?