[rurban]

The important number is the avg pause time. Here with ruby 2.1 7ms for a minor and 58ms for a major sweep for a typical ~500K heap app.

In my potion-based GC (a stack-scanning, compacting, cheney two-finger GC) the avg GC needs 3ms, but it's not concurrent (multi-threaded) yet.

All of these can be considered real-time, i.e. < 15ms. For bigger heaps the scans need to be incremental (saving and restoring GC state, which is easy with libgc or cheney).

The best java GC I found needed 150ms pause time. Good lisp's have real-time GCs.