It's very tricky...
Memory is adjusted automatically to the container size [1] (of course you may override it by supplying Xmx or "-n" as parameters [2]). The safe limit is roughly Xmx=Xms=50% of container capacity (unless you do the off-heap, that you can squeeze Infinispan much, much more).
Then there are Limits, Requests and QoS in Kubernetes [3][4]. We are in bustable memory category so if there is additional memory in the node, we'll get it. But if not, we won't go below 512 MB (and 500 mCPU).
Thanks,
Sebastian