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From "Leon Rosenberg" <rosenberg.l...@googlemail.com>
Subject Re: WebApp really slow, Where do I start looking?
Date Fri, 01 Jun 2007 15:38:51 GMT
start with monitoring. Find out which action/servlet/whatever is
taking time. Go further down and check where the time is spent (a
service object or something). Narrow it down, than solve it :-)

regards
Leon

>
> 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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> >
>
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