try!.......
vi /etc/httpd/conf.modules.d/00-mpm.conf
LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
vi /etc/httpd/conf/httpd.conf
<IfModule mpm_prefork_module>
StartServers 5
MinSpareServers 5
MaxSpareServers 10
ServerLimit 2000
MaxClients 1000
# MaxRequestWorkers 1024
MaxConnectionsPerChild 0
</IfModule>
KeepAlive off