DatagramChannel performance issue

[Martin Thompson]

We've been diagnosing a performance issue and isolated it to receiving
on a datagram socket
where we are seeing a significant step down in performance, and
increase in allocation, when
more than one source is sending.

https://github.com/frohoff/jdk8u-jdk/blob/master/src/windows/native/sun/nio/ch/DatagramChannelImpl.c#L138

When receiving from two or more sources we get InetAddress and
InetSocketAddress objects
allocated and they are set via multiple up calls from the JNI code into Java.

A much more efficient implementation would be one that passes down two
ByteBuffers.
One to be filled in for the payload and one for the header. Allocation
on a per packet receive
is not a useful design for a network API.

A read operation is not a valid alternative as we need the sender address.

Regards,
Martin...