I'm trying to set up a web server on a VPS. My problem is that memory usage of php-cgi processes increases over time even though the website is not receiving any traffic at all. (it is behind a firewall for the time being)
The VPS has 360MB RAM. I'm using Debian Lenny 32bit and its lighttpd and php5-cgi packages. Apart from some config changes (listed below), I'm using the stock setup by Debian.
The website is based on Drupal. Using Drupal's devel module, I can tell that memory usage of PHP scripts is less than 20KB on average, and it never exceeds 8MB.
Here are the relevant parts from the output of ps aux:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
www-data 29871 0.0 1.7 54552 6368 ? Ss Aug12 0:00 /usr/bin/php-cgi
www-data 29873 0.0 7.4 65808 27468 ? S Aug12 0:00 /usr/bin/php-cgi
www-data 29874 0.0 3.7 55808 13736 ? S Aug12 0:00 /usr/bin/php-cgi
www-data 29875 0.0 4.3 58040 16204 ? S Aug12 0:00 /usr/bin/php-cgi
www-data 29876 0.0 4.4 57444 16288 ? S Aug12 0:00 /usr/bin/php-cgi
www-data 29877 0.0 1.7 54552 6368 ? Ss Aug12 0:00 /usr/bin/php-cgi
www-data 29879 0.0 9.6 67140 35684 ? S Aug12 0:26 /usr/bin/php-cgi
www-data 29880 0.0 6.6 59172 24492 ? S Aug12 0:23 /usr/bin/php-cgi
www-data 29881 0.0 7.1 59784 26388 ? S Aug12 0:22 /usr/bin/php-cgi
www-data 29882 0.0 7.4 60880 27440 ? S Aug12 0:23 /usr/bin/php-cgi
- Is it normal to have php-cgi this large?
- Is it possible to estimate php-cgi memory usage based on settings?
- Any tips for reducing memory consumption of php-cgi processes?
Searching for known memory leaking bugs didn't yield anything relevant. And I'd be surprised if the default Debian packages/config had such an obvious memory leak. Other users on the same host do not have this problem.
What I've done so far is set PHP_FCGI_MAX_REQUESTS to a low value so that php-cgi processes are recycled quickly. When I use ab to simulate high load, this works very well. Processes die quickly before they grow higher than 10MB. However, under low-to-medium load, all processes grow steadily (because of load balancing) and most of them consume 28MB+ simultaneously, putting my VPS at risk of swapping. Please note than even without any sort of traffic, the processes grow steadily.
I can reduce the number of php-cgi processes, but this feels like a workaround more than a fix. I'd be surprised if php-cgi normally grew like this.
Also, summing the total RSS numbers for php-cgi processes gives:
$ ps -C php-cgi -o rss= | awk '{s+=$1}END{print s/1024}'
195.738
Yet, free -m gives the following output:
total used free shared buffers cached
Mem: 360 351 8 0 33 190
-/+ buffers/cache: 127 232
Swap: 255 0 255
- Am I missing something? How come the used memory (without buffers) is lower than the total resident memory of php-cgi processes on the host?
I have the following PHP extensions:
php5-cgi php5-common php5-curl php5-gd php5-mysql php5-xcache
xcache.size is set to 24M. It used to be 32M but reducing it didn't help. xcache.var_size is set to 0. The remaining plugins are using the stock configuration. The xcache admin pages shows that xcache is using less than 1MB.
PHP's memory_limit is set to 32M.
Here is my FastCGI config:
fastcgi.server = ( ".php" =>
((
"bin-path" => "/usr/bin/php-cgi",
"socket" => "/tmp/php.socket",
"max-procs" => 2,
"idle-timeout" => 20,
"bin-environment" => (
"PHP_FCGI_CHILDREN" => "4",
"PHP_FCGI_MAX_REQUESTS" => "1000"
),
"bin-copy-environment" => (
"PATH", "SHELL", "USER"
),
"broken-scriptfilename" => "enable"
))
)
I'm using more-or-less the stock lighttpd.conf that ships with Debian.
Please let me know if there is any other data that I can provide.
Any help is appreciated. I've been trying to troubleshoot this for days. I've run out of ideas.
