NIO outer heap memory and zero-copy

Ordinary memory model:

　　java thread memory -> operating system memory -> hard drive

Direct memory model:

　　java -> operating system memory -> hard drive

Comparison between the two, a little step: Direct Memory Direct operating system memory, this step is less java thread memory to memory copy of the operating system, it increases efficiency.

 

Memory-mapped files:

MappedByteBuffer: mapping files to java thread, can be directly manipulated. Specific read and write is still the responsibility of the system.