In reply to Mark Gavalda (@MarkGavalda).

Just like PHP-FPM you can run multiple HHVM processes as different users. It takes some manual work to set it up, but if you dig into /etc/init.d/hhvm you can see how the processes are initialized. Just create a new process that runs on a different port (just like with "pools" over TCP/IP on PHP-FPM).