Memory usage caused by MySQL or Apache?

Question

Here is a screenshot of my usage today on an idle unfinished cms drupal site with a maximum of 14 added modules besides core and no activity or users.

As you can see I am at my limit which is crazy so I need to limit memory usage of apache and mysql and php because my VPS is smallest one which should suit my current needs.

My system file my.cnf does not have a list of parameters as I've seen posted elsewhere but this is the file which apparently will lessen usage of memory amongst other things I've read like memory leaks and apache MPM workers vs apache prefork which seems to be what I have.

So how can I significantly reduce memory usage without removing apache or php5?

I am using mysql version 5.1.66 and looks like innodb and show variable yabbit.net/mysql.txt

Answer 1

I'm suspecting that your Apache configuration is the culprit here, instead of your MySQL configuration. The current MySQL settings should not get it beyond about 50MB total (typically even lower I think).

However, from the configuration of Apache you posted in the comments along with the fact that your VPS only provides 256 MB of memory, I see that a setting of

MaxClients       256

for the Prefork MPM is way too much for such a machine. On my Debian Squeeze webservers I see about 20MB usage per fork, so about 15 connections will already consume all the memory in your machine. It's not hard to get so many concurrent connections and as a result processes will be killed, probably, or a lot of swap will be used. Result: disfunctional server or slow service response respectively.

I suggest you to either:

• Scale down your prefork configuration significantly to for example this:

  <IfModule mpm_prefork_module>
      StartServers         10
      MinSpareServers      5
      MaxSpareServers      15
      MaxClients           15
      MaxRequestsPerChild  2000
  </IfModule>
  

  And live with the fact you can't serve more than about 8 concurrent visitors (usually two client connections per browser). This is a limitation of the amount of memory in combination with the chosen LAMP configuration.

• Move to PHP-FPM, set up a small pool and move to the worker MPM or even another web server such as nginx. The worker MPM uses threads that share memory, rather than forks, which don't. This should allow you to handle more concurrent visitors.