Furthermore they're using 2mb pages instead of the usual 4kb (on x86). That cuts the overhead by a factor of 512 alone. The remaining problem I see is cache-tr

Furthermore they're using 2mb pages instead of the usual 4kb (on x86). That cuts the overhead by a factor of 512 alone. The remaining problem I see is cache-trashing because on every minor page-fault you have to run a part of your mark&sweep algo, surely kicking out all the application data&code from caches. That's inevitable less efficient than a stop-the-world approach.