I've got 2 servers: my local server and remote production server. They've got basically the same config: Ubuntu 10.10, Apache 2, PHP 5.3, PHP-APC, MYsql etc. I also have copies of a webapp on both servers and here's the problem with PHP:
On my local server webapp uses only ~4 MB of memory, but on my production server memory usage spikes up to 50 MB of memory for no good reason. I tried to run memory_get_peak_usage() function to get memory usage at different stages of webapp execution and i've found that on production server memory spikes from 0.7 up to 49 MB on such function calls as class_exists().
What could be the problem?
Tanks.
Hate to sound a bore, but have you verified that they have exactly the same Apache/PHP config as they can easily become the source of these sort of differences..
Also are they experiencing the same sort of load, as code running on a server under load can behave very differently to code running with ample uncontested resources.
Are there any other differences in terms of other running applications that could be affecting stuff?
It maybe worth profiling the code on both the servers to see if there are any per-request differences, XHprof[1] is a great tool for this and it can safely be run in production (as long as you read the instructions)
[1] http://phpadvent.org/2010/profiling-with-xhgui-by-paul-reinheimer
Ok, i've found where was a problem. There is a class that was creating cache file containing information on user's browser (in order to recognize them later). Apparently there was a problem with that file and/or parser so it was using too much memory. Since then i've cleared cache files and if situation will repeat, i'll ditch that class altogether.
Thanks to all who answered/commented on problem.
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I've written some JS scripts on my school's VLE.
It uses the UWA Widget Format and to communicate with a locally-hosted PHP script, it uses a proxy and AJAX requests.
Recently we've moved the aforementioned locally-hosted server from a horrible XP-based WAMP server to a virtual Server 2008 distribution running IIS and FastCGI PHP.
Since then - or maybe it was before and I just didn't notice - my AJAX calls are starting to take in excess of 1 second to run.
I've run the associated PHP script's queries on PHPMyAdmin and, for example, the associated getCategories SQL takes 0.00023s to run so I don't think the problem lies there.
I've pinged the server and it consistently returns <1ms as it should for a local network server on a relatively small scale network. The VLE is on this same network.
My question is this: what steps can I take to determine where the "bottleneck" might be?
First of all, test how long your script is actually running:
Simplest way to profile a PHP script
Secondly, you should check the disk activity on the server. If it is running too many FastCGI processes for the amount of available RAM, it will swap and it will be very slow. If the disk activity is very high, then you know you've found your culprit. Solve it by reducing the maximum number of fastcgi processes or by increasing the amount of server RAM.
First I want to say that I'm using Drupal as CMS and I know that there is separate Drupal stackexchange site. But my problem is not Drupal specific, it's not in User or Advanced User level. It's PHP and Server related. OK now problem.
I have developed website which is not launched yet. Am getting out of memory errors random times. And sometimes server gets crashed. Helps rebooting. There is no other people using App so no heavy load. Particulary am exceeding privmmpages limit. I have tried some general things - increasing/decreasing PHP memory limit, looking in error logs, logging slow MySQL queries. Nothing... Same.
I have ran 'top' linux command. There is 4-5 apache processes depending on browser requests. Which MEM usage(%) are 10, 5, 4, 3, 0.5. two processes are running >10hr.
After restarting apache I got +40% free memory.
Here some questions and mysts for me.
Why that two processes are running so long when there is no active request from browser? And how can I prevent them?
Why I got +40% free memory after restarting when I had 10+5+4+3+0.5 memory used by apache? This should not be equal?
Can this be a memory leak? How can I detect them?
What techniques I should use to step down from higher levels to low levels? Imagine I have 'memory leak' in one of my function, how should I get him in whole application?
How can I benchmark my particulary functions for memory and CPU usage?
Why server is crashing? Even basic httpd restart is returning "fork: Cannot allocate memory". Can this be a symptom of memory leak?
Please answer point by point.
Sounds like you may have an infinite loop somewhere or your not releasing resources when dealing with things such as GD.
Linux keeps things in RAM while there is free ram, if there is a sudden need from another process for RAM, and the ram is not being held in use, Linux will free/swap it for the application in need. Check the output of "free" and you will notice a cached column that indicates how much is just cached and can be released at any time.
I develop a web server's PHP scripts to retrieve tiled images to cover Earth surfaces such as World Wind.
Suppose I have get_image.php that returns image/jpeg or image/png as the response.
The initial condition is also that I have Windows Server 2003 to test my script on and preinstalled Apache 2.2.16 with a thread model. So I had to install thread safe PHP 5.3 to use it as Apache's module.
After script has been succesfully written I decided to produce a load testing using JMeter. Starting with a single virtual user performing a request per no more than 0.5 seconds and increasing the number of virtual users every minute at the moment of nine virtual users I get some not handled requests though looking in server's Task Manager I see no more than 8-10% of CPU. The maximum performance I get is 1600-1700 successful responses per a minute (requests are produced by eight virtual users).
I am not a system administrator and not experienced dealing with heavy performances, so my question is: can this be a problem of PHP thread safety discussed here? How can I determine the problem I face? Would it be better to try my script as CGI with IIS + FastCGI or we have to look at Linux-based web server?
P.S. I also use memcached server and php_memcache.dll (so-called thread safe version) downloaded from http://downloads.php.net/pierre. This module is not officially supported for Windows and probably it's not really thread safe so it could cause an additional effect to my problem in the case of the problem described is PHP thread safe issue.
If I were you I would use XDebug to track down which parts of your application ar eating the time and causing the failed requests.
Since you are on windows ( i presume ) then you can use a handy little program called WinCacheGrind to open and review the output files. It will show you, line by line or function by function, exactly how long the different blocks of code in your application take to run.
If you find that there is nothing surprising in the grind then that is the time to start looking at the environment.
We are using Jmeter to test our Php application running on the Apache 2 web server. I can load up Jmeter to use 25 or 50 threads and the load on the server does not increase, however the response time from the server does. The more threads the slower the response time. It seems like Jmeter or Apache is queuing the requests. I have changed the maxclients value in apache web server configuration file, but this does not change the problem. While Jmeter is running I can use the application and get respectable response times. What gives? I would expect to be able to tax my server down to 0% idle by increase the number of threads. Can anyone help point me in the right direction?
Update: I found that if I remove sessions from my application I am able to simulate a full load on the server. I have tried to re-enable sessions and use an HTTP Cookie Manager for each thread, but it does not seem to make an impact.
You need to identify where the bottleneck is occurring, and then attempt to remediate the problem.
The JMeter client should be running on a well equipted machine. I prefer a Solaris/Unix server running the JVM, but for <200 threads, a modern windows machine will do just fine. JMeter can become a bottleneck, and you won't get any meaningful results once it does. Additionally, it should run on a separate machine to what your testing, and preferable on the same network. The WAN latency can become a problem if your test rig and server are far apart.
The second thing to check is your Apache workers. Apache has a module - mod_status - which will show you the state of every worker. It's possible to have your pool size set too low. From the mod_status, you'll be able to see how many workers are in use. To few, and Apache won't have any workers to process requests, and the requests will queue up. Too many, and Apache may exhaust the memory on the box it's running on.
Next, you should check your database. If it's on a separate machine, the database could have an IO or CPU shortage.
If your hitting a bottleneck, and the server and db are on the same machine, you'll generally hit a CPU, RAM, or IO limit. I listed those in the order in which they are easiest to identify. If you get a CPU bound app, you can easily see you CPU usage go to 100%. If you run out of RAM, your machine will start swapping. On both Windows and unix it's fairly easy to see your available free RAM. Lastly, you may be IO bound. This too can be monitored using various tools or stats, but it's not as obvious as CPU.
Lastly, specifically to your question, the one thing that stands out is it's possible to have a huge number of session files stored in a single directory. Often PHP stores session information in files. If this directory gets large, it will take increasingly long amount of time for PHP to find the session. If you ran your test will cookies turned off, the PHP app may have created thousands of session files for each user request. On a Windows server, it will slow down faster than on a unix server, do to differences in the way directories are stored on the two operating systems.
Are you using a constant throughput timer? If Jmeter can't service the throughput with the threads allocated to it, you'll see this queueing and blowouts in the response time. To figure out if this is the problem, try adding more threads.
I also found a report of this happening when there are javascript calls inside the script. In this instance, try to move javascript calls to the test plan element at the top of the script, or look for ways to pre-calculate the value.
Try checking a static file served by apache and not by PHP to see if the problem is in the Apache config or the PHP config.
Also check your network connections and configuration. Our JMeter testing was progressing nicely until it hit a wall. Eventually realized we only had a 100Mb connection and it was saturated, going to gigabit fixed it. Your network cards or switch may be running at a lower speed than you think, especially if their speed setting is "auto".
I'm helping out in a forum that runs on SMF. The site has been lagging recently and our host tells us it's the file uploads that clogs the servers memory and that SMF is using server memory in a non optimized way. There's probably one file upload every hour at most so the load isn't that high.
Any thoughts on this? I don't know php to the extent that i can argue against them.
If PHP is run as an Apache module, used memory will not always be returned when the PHP script ends. There are a couple of ways to fix this:
Use less memory in your script (obviously)
Run your script as CGI instead of as an Apache module (this way, the memory will be returned on script exit)
Restart Apache when the memory needs to be reclaimed. This is not really a good solution, but we do it at Levonline twice a day...
Upgrade your hosting to your own server, where you don't have to think about the hosting provider's other customers, and can use as much memory as you want.