CENTOS / HTTPD memory issue

Question

Hi I am running a VPS (1GB memory) which has a client site on it with these specs:

• Wordpress (no cache plugins)
• Timthumb image resize script (http://timthumb.googlecode.com/svn/trunk/timthumb.php)
• Shopp plugin for ecommerce (has a caching system)

Php.ini memory limit is set to 64M max per script

After restarting apache I have around 500M free memory. After only visiting this client's site in a random browser memory drops by 150-200M !!

I am trying to figure out the loophole, but I might be overlooking the obvious awnser please advise :-)

Answer 1

I'm assuming you're on a Linux VPS, so ... how are you looking at 'free' memory? There's a few different measures of that in your average Linux system. For instance, from my Linux box, I get:

marc@panic:~$ free
             total       used       free     shared    buffers     cached
Mem:       2058188    1596532     461656          0     778404     604752
-/+ buffers/cache:     213376    1844812
Swap:      1052248          0    1052248

By the first line, it would appear that 1.5gig are in use and just under 500meg are free (on a 2gig box). However, those totals include memory used for disk cache, which is the second line. Once you remove cache buffers from the counts, then only 213meg of memory are used by running processes, and 1.8gig are free.

Answer 2

When you have started apache, the various php process that are idle around occupy only about 10MB of memory. The number of php process depends on how many server / childs do you have.

When you access your site, PHP is executing, and increse is memory size. Tipically you end up with a PHP process that is about 50-60 MB each.

To verify type in your shell

ps -ylC apache2

and see the column RSS. Substiture apache2 with the process name of your http server

Do it after a fresh start and after visiting your site!