Linux under the Apache httpd process old dead __linux

The company's test server, is also public, hanging on the test server domain name outside is accessible, recently found that the page access is very slow, sometimes, half a day can not open. Look for a reason.
1, my first reaction is not the server system resources are not enough, SSH login up to look at, memory, CPU, bandwidth is enough, not this reason.
2, check the Apache error log logs, there is no obvious cause of httpd to slow down.
3, is not the number of httpd connection, check it.
Apache is prefork mode, the maximum number of connections in the configuration file is 256, the actual is 257, so there will always be a meeting.
[Root@rudder conf]# Apachectl-l
Compiled in Modules:
Core.c
Prefork.c
Http_core.c
Mod_so.c

[Root@rudder conf]# Ps-e|grep httpd|wc-l
257
I checked the zombie process, and there was a httpd zombie there.
HTTPD Zombie Process
HTTPD Zombie Process
The solution is as follows:
1, modify vim/etc/httpd/conf/httpd.conf