Defunct processes bogging down server

[ludachris]

I've noticed more and more database errors lately, and I believe our server should be able to handle the load our site creates. I have a server admin who helps out from time to time and he pointed out how the server has a lot of defunct processes going on all the time. He said on average, defunct processes are taking up 30% of the server's resources. Here's a list of the top 10 processes that were going on yesterday, about an hour after a reboot:

~$ ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10
%CPU PID USER COMMAND
44.0 12493 10003 [php-cgi] <defunct>
22.2 5197 mysql /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock
1.7 12461 www-data /usr/sbin/apache2 -k start
1.4 12268 10003 [php-cgi] <defunct>
1.3 12308 10003 [php-cgi] <defunct>
116 12489 10003 [php-cgi] <defunct>
1.1 11568 www-data /usr/sbin/apache2 -k start
0.8 9076 www-data /usr/sbin/apache2 -k start
0.8 12159 www-data /usr/sbin/apache2 -k start

Any idea how exactly to track down what scripts are running these processes? My server guy said that it would take a LONG time to figure out. I just need to know exactly how to track it down, what to look for and what actions I need to take once I do figure it out. Any other suggestions on actions I can take to optimize and improve the server performance? We are already running a caching solution on the server.

Thanks in advance!