The JVM will start with memory useage at the initial heap level. If the maxheap is higher, it will grow to the maxheap size as memory requirements exceed it’s current memory.
So,
- -Xms512m -Xmx512m
JVM starts with 512 M, never resizes.
- -Xms64m -Xmx512m
JVM starts with 64M, grows (up to max ceiling of 512) if mem. requirements exceed 64.