On Fri, Mar 9, 2012 at 8:07 AM, Simone Frattegiani <simone.frattegiani@xxxxxxxxx> wrote: > Hello, > > i suddendly started having CPU load issues, like this: A couple of things: > Server-status shows this: > > […] > ReqPerSec: 6.37383 > BusyWorkers: 99 > IdleWorkers: 10 > Scoreboard: WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW > This is what worries me. You are handling 6.3 requests per second, but have 100 active workers handling requests. This means your requests are really, really slow. When requests are really slow, and the server gets a little busy, two things happen: 1) Requests take even longer to serve, as the resource contention (probably database) increases 2) Apache has to serve more simultaneous requests, and so has to have more children, which uses more CPU to start and run the processes, and more RAM is used on the new process. When this reaches the tipping point, which can be due to not enough RAM, not enough CPU, not enough IOPs, Apache has to start processes faster than it can serve requests, and load will metaphorically explode. > […] > The commands "netstat -a | grep 66.249" shows 20 connections from > googlebot ip, 1 in ESTABILISHEd status, the others in TIME WAIT. > So this may be largely irrelevant. If they are all in TIME_WAIT, then that is a keep alive connection. A keep alive connection isn't using your CPU, so it isn't slowing down your webserver. What it is doing is taking up a slot, which isn't ideal. > If i restart apache, everything gets back to normal. > > Any suggestions? > THanks! > I have a couple! First of all, you are using prefork MPM. This means to get an extra slot, apache has to fork and start up a new child. This is not efficient! If you use the worker or event MPM, then each child has multiple threads, and so you do not require to start, or keep starting, so many children. You will also have less CPU/RAM costs per slot. This will stop CPU usage exploding when a lot of requests come in, and hopefully you can serve requests faster. Finally, if you are worried about keep alive connections from google bot, you should seriously consider event MPM. This will use a single thread to handle ALL keep alive connections, waiting for a new request on it, and handing the request off to a different thread once there is data. This means you don't use multiple slots to handle keep alive connections. Finally, you don't mention it, but I assume you are running some web application, like PHP? I would recommend using fastcgi to host the application, divorce it entirely from apache. This will give you a clear idea of how much of your resources are being devoted to PHP, and will actually reduce the amount of resources over using mod_php. mod_php adds a PHP interpreter in every apache child, whether it is serving a PHP request, a static file from disk, or monitoring a keep alive connection. You can also strictly control how many PHP processes are used when running with fastcgi. Cheers Tom --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx
|