Centos – Too many apache processes in D state

take a loog at this Apache doc: http://httpd.apache.org/docs/2.0/mod/mpm_common.html#maxclients With this you can regulate your maximum number of processes.

When your tomcat/app is working as it should tomcat releases the connection. Make sure your webapp is not blocking the connections by doing too long requests to a backend or something else.

Christian

You're almost certainly running mod_php, which means you're almost certainly running apache in mpm_prefork.

If performance is generally okay until load causes you to start swapping, a quick fix is to start throttling down apache's MaxClients. If apache is allowed to fork worker processes whenever it wants, it's going to start swapping under load. Requests will queue until a worker is available, so things can get slow, but not as slow as the death-by-swap.

If you really need to tune things tighter, consider getting away from prefork apache mpm. That means running PHP as FastCGI. If you're going to go with PHP under FastCGI, you should consider upgrading to PHP 5.3.3, which has much nicer FastCGI process manager (--enable-fpm configure option).

php-fpm/worker is much more memory efficient than old-fashioned mod_php. You can then tune the number of apache processes/threads independently of the number of PHP processes. And your memory-heavy PHP processes are only used for serving up php-driven content, and not wasted on serving static files.