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From "Larry Meadors" <lmead...@apache.org>
Subject Re: WebApp really slow, Where do I start looking?
Date Fri, 01 Jun 2007 14:11:30 GMT
Are the database and the tomcat server on the same machine?

Can you explain a little more about your synchronized code? I have
done several really big web apps with iBATIS, and haven't needed to
sync anything...

Larry


On 6/1/07, Stéphane Hanser <s.hanser@omegames.com> wrote:
> You are right about synchronized blocks. I removed every synchronized
> instruction for tests purposes and it "unleashed the cpu" ;)
>
> It may be a problem with memory too. By disabling the cache of iBatis I
> noticed an overloading of the CPU, which is understandable considering the
> circumstance.
>
> However, removing some synchronized blocks will cause concurrent access
> issues when a user "mass clicks". Is it possible to configure tomcat to
> queue one's requests instead of executing the in parallel ?
>
> Thanks,
>
> Stéphane H.
>
> PS: thanks for the jmeter tip ;)
>
>
> -----Message d'origine-----
> De: David Delbecq [mailto:delbd+jakarta@oma.be]
> Envoyé: vendredi 1 juin 2007 10:59
> À: Tomcat Users List
> Objet: Re: WebApp really slow, Where do I start looking?
>
> Considering CPU usage, it is not
> 1) a java memory problem, if java memory was full, garbage collector
> would start using lots of cpu
> 2) a time consuming java code.
>
> It might be one of following
> 1) synchronized blocks in your code, that would prevent 2 simultaneoous
> users from doing some operations.
> 2) use of SingleThreadModel, which has same effect as above
> 3) Network congestion, you server simply can't send the response to
> client due to a too small network pipe (80 requests / second resulting
> each in an about 20k response need a bandwidth of more than 12Mbits)
> 4) A too small physical memory on system. Eg you configure tomcat to use
> 1G memory but your server has only 512M available, resulting in memory
> pagination (swap) and sleeping of java process during pagination process
> (typically, on unix server, you will see a high % of CPU dedicated to
> system instead of idle when this happen)
>
>
> One way to test your server performance during heavy is to use apache
> jmeter.
>
>
> En l'instant précis du 01/06/07 10:48, Stéphane Hanser s'exprimait en
> ces termes:
> > Hello,
> >
> > I've been working on my project for months now, it is my first WebApp
> > project. Yesterday, I deployed the project on my dedicated server and
> > a soon as I reached about 80 users, the webapp became really slow.
> > However, the cpu usage of the server was very low (never more than
> > 15-20%). I have no idea of what is the cause of this slowness (server
> > config, bad programming..).
> >
> > Can someone help me to diagnostic the problem? Where shoul I start
> > looking?
> >
> > thanks in advance,
> >
> > Stéphane H.
> >
> >
> >
> >
> >
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>
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>
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