FR System Memory usage question

Hi. Strange situation happen at all FR2.1.6,2.1.7,2.1.8, and 2.2.0(git) version the situation is radiusd are use all system available memory radiusd is using about 10 request processing 1Mb system memory "add only not returned memory space" so, at last radiusd is using all system memory..and memory fault and die radiusd. if stop radiusd then using system memory is roll back if restart radiusd then memory roll back and ... very strange, FR2.2.0(git) immediate restart radiusd but roll back is not. whats wrong?(FR 1.X version is not happen situation) My OS is CentOS 5.2, backend mysql Thanks.