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

There are many reasons why this could happen. Without code and/or more details about the data, we can only guess what is happening.

Some Guesses:

• Maybe you hit the maximum bytes that can be read at a time, thus the IOwaits gets higher or memory consumption up without a decrease in loops.
• Maybe you hit a critical memory limit, or the JVM is trying to free memory before a new allocation. Try playing around with the -Xmx and -Xms parameters
• Maybe HotSpot can't/won't optimize, because the number of calls to some methods are too low.
• Maybe there are OS or Hardware conditions that cause this kind of delay
• Maybe the implementation of the JVM is just buggy ;-)