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I'm having problem with my webserver which is currently running with very high loads. There are no cron jobs running and I can see any processes using the CPU. How can I find out what is going on?

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migrated from stackoverflow.com May 9 '11 at 11:15

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2 Answers 2

From your top output it looks like the issue is high IO (RAM/CPU usage is low, IOWait% is high, load is high, and several httpd processes with state 'D'). What sort of application are you running? Are you using a database layer like MySQL? If so, what sort of load is the database experiencing and is it configured/optimized correctly?

You can try running iostat -x 5 when the IOWait% is high to see which drive is being used and whether it is read/write heavy. The next, more time consuming, step is to figure out what the source of the IO load is and how to fix it.

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as i can see you are using apache prefork configuration and you have lots of clients on your server. start by trying to restart apache by typing sudo /etc/init.d/apache stop and then sudo /etc/init.d/apache start. you might consider switching to apache mpm configuration, so that you won't have so many process and load will be distributed across threads this way you might see the bottleneck processes that consume cpu time and kill them off or trace them out.

an alternative approach is to switch to lighthttpd or nginx web servers, they both consume less memory and can handle more simultaneous clients

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or gatling (very fast) –  thejh Nov 19 '10 at 20:53
    
Ok, thank you for the answer. I will try the solutions you described. –  Martin LeBlanc Nov 19 '10 at 21:50
    
The nginx and lighttpd solutions as described in your answer is not complete, those applications cannot run PHP, but need fastcgi for it (for PHP, php-fpm is recommended) –  Lekensteyn May 9 '11 at 11:32

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