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Date: Wed, 17 Oct 2012 09:28:30 +0100
From: Mark Thomas <markt@apache.org>
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To: Tomcat Users List <users@tomcat.apache.org>
Subject: Re: asking advice for tomcat 7 config
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On 17/10/2012 07:59, Romain Van der Keilen wrote:
> Hi There,
> 
> I'm quiet new to this mailing list as I encounter some configuration
> problems with Tomcat 7.0.30.

It is unlikely to help but you may as well upgrade to 7.0.32.

> We are currently developing a web
> application, and we wish to have a good response time with about 200
> parallel sessions. My problem is that starting from 70 users, the
> system does not respond quietly. At 70 users, we have an average of
> 4000ms for the response time. At 120 users we are at an average of
> 20000ms and with 200 users we have about 45000ms of response time.
> All of those numbers were computed with JMeter, using 4 passes.

I have seen very strange results with JMeter under load, particularly on
Windows. The results you are seeing may not be entirely correct. I get
better results (although less control) with ab on Windows. Or I run
JMeter on Linux.

> When the server is under a big load, what I could see with VisualVM
> is that the heap size used never exceed 500Mb. When 500Mb is reached,
> it drops back to about 100Mb. Another thing is that the CPU never
> works more than 5% of its capabilities.

That suggests that the app is not CPU bound.

> I also took a look at the CPU
> usage in java classes,

Using what>

> and there I saw that 95% of the time goes to
> org.apache.tomcat.util.threads.TaskQueue.take().

That is normal and means for 95% of the total thread processing time,
threads are waiting for the next task to process. It is the other 5% you
want to concentrate on.

> The first class
> related to my application is the oracle.net.ns.Packet.receive() and
> is at 0.1% of the CPU time ...
> 
> I've looked on a lot of forums to try to tune my tomcat
> configuration, but I haven't found anything that could really help
> me, this is the reason I ask to you. I've just put you the whole
> server.xml file after this, hoping you can have a look and tell me if
> there is some big issue with it... The only thing I changed is the IP
> of the server.

Profiling is the way to go to fix this and it looks like you are heading
in the right direction however you may need some better tools.

Mark

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