Max Clients Calculation - by http://www.shaolintiger.com

First find out the largest httpd process, change the httpd to apache2 if that's your thread name.

ps -aylC httpd |grep "httpd" |awk '{print $8'} |sort -n |tail -n 1

You'll get a number like 55687 - divide this number by 1024 to get megabytes - 54.38 MB.

After this stop apache (/etc/init.d/httpd stop or similar).

Then find out the free memory.

free -m |head -n 2 |tail -n 1 |awk '{free=($4); print free}'

You'll get a number like 2561 - this is already in Megabytes.

You can restart Apache now.

The final calculation for MaxClients is the second number divided by the first (free memory divided by max thread size).

eg. 2561/54.38 = 47 

So MaxClient would be 47 or 50 is fine.

This will prevent your machine getting memory locked by too many Apache processes.