The usage rate of Ambari Old memory is almost 100%, and cannot return to normal levels

A large number of HTTP requests to access Ambari over a period of time，the usage rate of Ambari Old memory is almost 100%. When stopping HTTP requests， the useage memory cannot return  to normal levels.

I executed command： jmap -histo:live | grep Session, and found the number of Session instances is close to 20000，and maintain this level for a long time（sometim more than one day）.  Under normal circumstances, the number of this object will not exceed 2000