Thank you so much for all your helpful advice! I'll take a few days to review all your suggestions and anylize the problem, and i will let you know as soon as i'll have news! Cheers :) On Fri, Mar 9, 2012 at 2:01 PM, Tom Evans <tevans.uk@xxxxxxxxxxxxxx> wrote: > 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 > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx
|