[jboss-jira] [JBoss JIRA] Created: (JGRP-815) Scatter/Gather to avoid copying

[Bela Ban (JIRA)]

Scatter/Gather to avoid copying
-------------------------------

                 Key: JGRP-815
                 URL: https://jira.jboss.org/jira/browse/JGRP-815
             Project: JGroups
          Issue Type: Feature Request
            Reporter: Bela Ban
            Assignee: Bela Ban
             Fix For: 2.8


When we invoke Channel.send(), we pass a bufffer to JGroups. At the transport level, JGroups marshals the sender and destination address, plus all headers and the buffer into a new byte[] buffer, which is then passed to the socket (DatagramSocket, MulticastSocket, Socket).

We cannot do gathering writes on a DatagramSocket because DatagramSocket doesn't expose this functionality, contrary to a DatagramChannel.

We could avoid having to copy the user's buffer by using gathering writes: effectively passing to the socket NIO ByteBuffers containing:
1: Src and dest address plus flags, plus possibly size
2: The marshalled headers
3: The buffer passed to JGroups by the user

We can obtain a gathering-write channel as follows:

ByteBuffer[] buffers; // contains the 3 byte buffers above
DatagramSocket sock;
DatagramChannel ch=sock.getChannel();
ch.write(buffers, 0, length); // length is the number of bytes of the total marshalled message

This is supported by a GatheringByteChannel.

I don't think there's currently a need to do scattered reads, but this needs to get investigated more. Also investigate whether MulticastSockets support gathering writes (whether they expose the correct DatagramChannel).


-- 
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators: https://jira.jboss.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira