-Xms2048m -Xmx4096m
Xms 初始堆大小 Xmx 最大堆大小
給了我個提示：
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option PermSize=2048M; support was removed in 8.0
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=2048m; support was removed in 8.0
所以，只需要給最大堆內存和初始堆內存就可以了。