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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject RE: Question on Performance Tuning
Date Wed, 19 Nov 2008 04:27:55 GMT
> From: Vasanth Kumar ravi [mailto:josvasanth@gmail.com]
> Subject: Question on Performance Tuning
>
> We did take thread dumps while performing the test, and
> found nothing related to application bottlenecks.

Thread dumps are appropriate for diagnosing hangs, but they're not terribly useful for analyzing
CPU usage.  You'd be better off running a profiler to see where time is being spent.  Even
the JVM's built-in hprof running in sample mode should give you a pretty good idea of where
the cycles are going (or use JVisualVM).

> Can I get some pointers on anything to be tuned in
> the tomcat to reduce the cpu utilization.

First, find out what's really using the CPU before fiddling with anything.  Tweaking Tomcat
is not likely to change much assuming the thread pool and heap are adequate for your load.

You've specified several GC options that may or may not be appropriate.  Unless you've proven
that changing NewRatio, NewSize, MaxNewSize, and SurvivorRatio actually helps your throughput,
you're likely better off leaving them alone.  128M MaxPermSize may be too small if you have
a lot of classes in your webapps.  Enabling concurrent GC produces more regular response times,
but will actually *reduce* throughput in most cases.

These might help slightly:
* Remove AspectJ.
* Turn off PrintGCDetails.
* Remove unused webapps.
* Precompile JSPs.
* Turn off auto-deployment.
* Turn off monitored resources.
* Set the parameters for the JSP servlet (in conf/web.xml) for production.

 - Chuck


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