Why the odd performance curve differential between ByteBuffer.allocate() and ByteBuffer.allocateDirect()

Question

I\'m working on some SocketChannel-to-SocketChannel code which will do best with a direct byte buffer--long lived and large (tens to hundreds of me

Answer 1

I suspect that these knees are due to tripping across a CPU cache boundary. The "non-direct" buffer read()/write() implementation "cache misses" earlier due to the additional memory buffer copy compared to the "direct" buffer read()/write() implementation.