Cluster performance degradation

Hi,

We are trying to validate the cluster performance based on number of read and write operation.
RadarGun tool used for performance measurement.

RadarGun is configured as below,

• Number of Thread accessing the Cache : 40
• Number of Entry per thread : 100000
• Read/Write Ratio : 60-40
• Cluster size : 5

There is a big dip in the performance while size of the entry is increased.
Approximately 17K tps ( for 1K size entry) is decreased to 3K tps (for 4K size entry) and also cluster becoming very unstable.

Attached the infinispan and jgroups configured with this post.

Will these configuration are OK or does it requires any tuning.

Regards,
Vadivel G