Apache taking up all CPU Time

[Samuel Vogel <samy-delux@xxxxxx>]

I'm running apache with about 4.000 vHosts on a DualCore 2,6 Opteron 
with 4GB of memory. I'm wondering why Apache takes up all my CPU time:

top - 12:30:56 up 3 days, 20:42,  1 user,  load average: 17.70, 18.06, 17.96
Tasks: 322 total,  22 running, 298 sleeping,   0 stopped,   2 zombie
Cpu(s): 98.2%us,  1.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.8%si,  
0.0%st
Mem:   4155428k total,  3934212k used,   221216k free,    30188k buffers
Swap:  2104496k total,    96916k used,  2007580k free,  2561980k cached

 PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  
COMMAND           
11075 www-data  25   0 99.8m  64m 4176 R   96  1.6 512:46.77 
apache2           
10914 www-data  25   0   99m  65m 4768 R   50  1.6 515:12.66 
apache2           
11055 www-data  25   0 99.9m  65m 4480 R   48  1.6 507:42.93 
apache2           

How can I debug where the problem lies? I'd be very grateful for any help!

Regards,
Samy

---------------------------------------------------------------------
The official User-To-User support forum of the Apache HTTP Server Project.
See <URL:http://httpd.apache.org/userslist.html> for more info.
To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx
  "   from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx
For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx