The idle process does not destroy when request finished

[DanYun Liu]

As the visit user is growing fast, I switch the method=threaded to method=prefork to handle more quest. But the service then become not available sometimes, I found that one or two processes were created  every minute and the old ones  still here with CPU usage 0%, idled. 

I don't have any idea where I can debug the problem, can anyone share some suggestions? 

thanks

--
Pursuit the freedom of the soul.