I'm running a 4 nodes cassandra cluster of VMware ubuntu instances each 768MB memory (on a single machine for development purposes). I need to reduce heap size appropriately as my nodes have been crashing at times with OOMs. How do I configure for this ? I think I would need to make some tweaks with MAX_HEAP_SIZE & HEAP_NEWSIZE in cassandra-env.sh !? but I not sure what should be the correct values I should put here for my case.