RAM problem with apache and PHP on default centos configuration

[Enrico Daga <enricodaga@xxxxxxxxx>]

Hi all,

I send this mail to both httpd and php lists.
I experienced the following problem running php scripts on httpd.
The RAM fills gradually until the system starts swapping, then, if I
don't restart the server, swap fills and everything goes down.
After some try/check tests, I realized that the memory used by a
single request is never released when the process is complete. This
makes the RAM to be gradually filled.
I thought in the beginning was a problem with the php application and
circular references on objects (I found some posts about this) then I
tried with a simple script (just populating a single array) but the
problem still occurs.
Our production environments are on Centos 4.9 - we have some legacy
applications that prevented us to upgrade the servers before.
For this sake I tried on fresh systems and more recent versions, and
experienced the same problem on Centos 4.9, 5.5 / PHP 5.1.6 and Centos
6 / PHP 5.3.6, with distributed packages for both httpd and php and
default configuration. Httpd uses the Prefork MPM module.
I also noticed that this _do not_ happen on Ubuntu 11.10 server. I had
a look at the configuration of both httpd and php, but in both cases
(Centos and Ubuntu) I could not noticed a difference on parameters
regarding memory usage.

Since this is the first time we run PHP applications on our httpd
servers I guess there is some configuration I should modify to have
the system behave correctly (free the memory when it is not needed).
The only workaround would be to move the MaxRequestsPerChild parameter
to 1, then killing the sub-process that hold the request, but I don't
believe this is the right solution.
Finally, I am not so sure that the issue I describe here belong to the
httpd or php lists, in this case please apologies, I would be very
happy if you can point me to a red-hat list (found a lot of lists, but
no sure which is related to httpd/php issues).

Thank you very much for any hint.

Best regards,
Enrico



-- 
Enrico Daga

--
http://www.enridaga.net
skype: enri-pan