The old rule of thumb is that with GC one needs at least twice the memory than the max live heap. With little free space GC disables a lot of possible optimizat

The old rule of thumb is that with GC one needs at least twice the memory than the max live heap. With little free space GC disables a lot of possible optimizations that bigger free space allows. Another Java-specific rule is that with heaps over 1-2GB one must think how to make data structures GC-friendly or how to split the application into separated processes. I guess the example program violated both of these.