high "Load Average"

[Sessna]

I am using nginx + php-fpm (quad-core PC) + MySQL (on another PC) and facing an interesting issue:
after some time nginx is running, system "load average" goes up (sometimes up to 30 and even more points) while CPU usage is still less then 30% With such a high load system becomes very slow and unresponsive. Restarting nginx helps, but only for a little while. Any ideas on the matter?

Thanks,
Sessna

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,63176,63176#msg-63176