A patch created by Gordon Sim will allow the connection to batch up outbound messages, resulting in less calls to the socket's write method (as more data is passed with each write).
This results in a small performance improvement. For example, given a broker with a single queue (flow control disabled), qpid-send filling it and qpid-receive draining it simultaineously with 300 byte messages:
qpid-send= 77581 msg/sec
qpid-receive= 77345 msg/sec
qpid-send= 84931 msg/sec
qpid-receive= 84789 msg/sec