I've just been learning about OSv from Cloudius Systems. More than just a single address space they have a single process (intended to run as a KVM guest). It m

I've just been learning about OSv from Cloudius Systems. More than just a single address space they have a single process (intended to run as a KVM guest). It makes some interesting optimizations possible and they get some incredible results: memcached, unmodified, runs faster in their KVM guest than it does on the bare metal. It seems limiting at first, but for the right use case their approach is really worth a look.