为什么ES的heap分配不要超过32G

The basic reason for this is that the JVM uses what is called HEAP memory for storing object pointers. In order to be more efficient, Java uses what’s called a Compressed Ordinary Object Pointer (OOP). Above 32 GB of HEAP, Java needs to use regular, 64 bit, pointers. This actually drastically decreases how many objects can be stored in HEAP to the point where around 50 GB of HEAP is about the same as around 30 GB.