Regression between 3.2.x and 3.3.x/3.4.x in Infinispan read simulation

Comparing JGroups 3.2/3.3/3.4 performance with Radargun, the throughput of reads in scenario simulating Infinispan went down by ~10%. See the attached chart.

• getall: the get request is sent to single node (randomly picked owner)
• getfirst: the get requests are sent to 2 nodes with ResponseMode.GET_FIRST - the second response is discarded.

Suspects:

Erik Salter profiled his application and noticed that the message parsing in the UDP receiver thread seemed to slow things down. He wrote a patch that brought his throughput back to 3.2 levels: https://github.com/an1310/JGroups/compare/t_perfhack

The UDP receiver thread may not tell the whole story, however: in the Radargun tests, performance with his patch was even lower.