These tricks have been used for a while in the JVM world. Here's a JVM equivalent of Hammerspace: http://www.mapdb.org/ And here's some slides concerning off-heap optimisations in Cassandra: http://www.slideshare.net/jbellis/dealing-with-jvm-limitatio...
On the JVM GC time is usually only an issue when the heap gets over 2GB or so. MRI's GC is not in the same league as the JVM's, but even so, 80MB should be easily handled. As such I'm guessing the memory consumption of multiple processes is causing the main issue, which would be solved if Ruby had real threads. JRuby has real threads, and many other language runtimes do as well. It seems like a lot of engineering effort is going into working around the deficiencies of MRI, a problem that can be easily solved by switching to something better.