httpd memory release is slow - apache

Question

I am using httpd with mod jk 1.2.28 on RHEL5.
Behind httpd, I do have tomcat running. Connection from httpd to tomcat is made via ajp connector using modjk.
I am just load testing the httpd - Using JMeter, when I create 2000 users in 120 seconds from two different JVMs simultaneously, the httpd memory usage goes high and when all the connections are released slowly, the httpd memory release is very slow. Sometime I do need to restart httpd process. When I restart httpd, memory usage immediately goes down.
What should I do to speed up httpd memory release without restarting httpd process ?
Is there any attribute for achieving this in workers.properties and httpd.conf ?
Please provide some help.
Thanks in advance :)

Answer 1

One interesting observation of mine -
With low value say 200 of maxThread in tomcat server.xml, httpd becomes unresponsive and I need to restart httpd after running my jmeter load test. Memory is not released automatically after the test completes
connections on 8009 are CLOSE_WAIT
With high value say 2000 of maxThread in tomcat server.xml, no need to restart httpd after running JMeter load test, As Memory is released automatically after the test completes
Connections on 8009 are LAST_ACK
My httpd.conf is as follows. I do not understand which of these two MPMs is used. Accordingly I need to modify MaxClient value. Please help I do not want to restart httpd and I dont want high value for maxThread.
<IfModule prefork.c>
StartServers 8
MinSpareServers 5
MaxSpareServers 20
ServerLimit 256
MaxClients 256
MaxRequestsPerChild 4000
</IfModule>
<IfModule worker.c>
StartServers 2
MaxClients 150
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>